Purdue Online Writing Lab Purdue OWL® College of Liberal Arts

Writing a Literature Review

OWL logo

Welcome to the Purdue OWL

This page is brought to you by the OWL at Purdue University. When printing this page, you must include the entire legal notice.

Copyright ©1995-2018 by The Writing Lab & The OWL at Purdue and Purdue University. All rights reserved. This material may not be published, reproduced, broadcast, rewritten, or redistributed without permission. Use of this site constitutes acceptance of our terms and conditions of fair use.

A literature review is a document or section of a document that collects key sources on a topic and discusses those sources in conversation with each other (also called synthesis ). The lit review is an important genre in many disciplines, not just literature (i.e., the study of works of literature such as novels and plays). When we say “literature review” or refer to “the literature,” we are talking about the research ( scholarship ) in a given field. You will often see the terms “the research,” “the scholarship,” and “the literature” used mostly interchangeably.

Where, when, and why would I write a lit review?

There are a number of different situations where you might write a literature review, each with slightly different expectations; different disciplines, too, have field-specific expectations for what a literature review is and does. For instance, in the humanities, authors might include more overt argumentation and interpretation of source material in their literature reviews, whereas in the sciences, authors are more likely to report study designs and results in their literature reviews; these differences reflect these disciplines’ purposes and conventions in scholarship. You should always look at examples from your own discipline and talk to professors or mentors in your field to be sure you understand your discipline’s conventions, for literature reviews as well as for any other genre.

A literature review can be a part of a research paper or scholarly article, usually falling after the introduction and before the research methods sections. In these cases, the lit review just needs to cover scholarship that is important to the issue you are writing about; sometimes it will also cover key sources that informed your research methodology.

Lit reviews can also be standalone pieces, either as assignments in a class or as publications. In a class, a lit review may be assigned to help students familiarize themselves with a topic and with scholarship in their field, get an idea of the other researchers working on the topic they’re interested in, find gaps in existing research in order to propose new projects, and/or develop a theoretical framework and methodology for later research. As a publication, a lit review usually is meant to help make other scholars’ lives easier by collecting and summarizing, synthesizing, and analyzing existing research on a topic. This can be especially helpful for students or scholars getting into a new research area, or for directing an entire community of scholars toward questions that have not yet been answered.

What are the parts of a lit review?

Most lit reviews use a basic introduction-body-conclusion structure; if your lit review is part of a larger paper, the introduction and conclusion pieces may be just a few sentences while you focus most of your attention on the body. If your lit review is a standalone piece, the introduction and conclusion take up more space and give you a place to discuss your goals, research methods, and conclusions separately from where you discuss the literature itself.

Introduction:

  • An introductory paragraph that explains what your working topic and thesis is
  • A forecast of key topics or texts that will appear in the review
  • Potentially, a description of how you found sources and how you analyzed them for inclusion and discussion in the review (more often found in published, standalone literature reviews than in lit review sections in an article or research paper)
  • Summarize and synthesize: Give an overview of the main points of each source and combine them into a coherent whole
  • Analyze and interpret: Don’t just paraphrase other researchers – add your own interpretations where possible, discussing the significance of findings in relation to the literature as a whole
  • Critically Evaluate: Mention the strengths and weaknesses of your sources
  • Write in well-structured paragraphs: Use transition words and topic sentence to draw connections, comparisons, and contrasts.

Conclusion:

  • Summarize the key findings you have taken from the literature and emphasize their significance
  • Connect it back to your primary research question

How should I organize my lit review?

Lit reviews can take many different organizational patterns depending on what you are trying to accomplish with the review. Here are some examples:

  • Chronological : The simplest approach is to trace the development of the topic over time, which helps familiarize the audience with the topic (for instance if you are introducing something that is not commonly known in your field). If you choose this strategy, be careful to avoid simply listing and summarizing sources in order. Try to analyze the patterns, turning points, and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred (as mentioned previously, this may not be appropriate in your discipline — check with a teacher or mentor if you’re unsure).
  • Thematic : If you have found some recurring central themes that you will continue working with throughout your piece, you can organize your literature review into subsections that address different aspects of the topic. For example, if you are reviewing literature about women and religion, key themes can include the role of women in churches and the religious attitude towards women.
  • Qualitative versus quantitative research
  • Empirical versus theoretical scholarship
  • Divide the research by sociological, historical, or cultural sources
  • Theoretical : In many humanities articles, the literature review is the foundation for the theoretical framework. You can use it to discuss various theories, models, and definitions of key concepts. You can argue for the relevance of a specific theoretical approach or combine various theorical concepts to create a framework for your research.

What are some strategies or tips I can use while writing my lit review?

Any lit review is only as good as the research it discusses; make sure your sources are well-chosen and your research is thorough. Don’t be afraid to do more research if you discover a new thread as you’re writing. More info on the research process is available in our "Conducting Research" resources .

As you’re doing your research, create an annotated bibliography ( see our page on the this type of document ). Much of the information used in an annotated bibliography can be used also in a literature review, so you’ll be not only partially drafting your lit review as you research, but also developing your sense of the larger conversation going on among scholars, professionals, and any other stakeholders in your topic.

Usually you will need to synthesize research rather than just summarizing it. This means drawing connections between sources to create a picture of the scholarly conversation on a topic over time. Many student writers struggle to synthesize because they feel they don’t have anything to add to the scholars they are citing; here are some strategies to help you:

  • It often helps to remember that the point of these kinds of syntheses is to show your readers how you understand your research, to help them read the rest of your paper.
  • Writing teachers often say synthesis is like hosting a dinner party: imagine all your sources are together in a room, discussing your topic. What are they saying to each other?
  • Look at the in-text citations in each paragraph. Are you citing just one source for each paragraph? This usually indicates summary only. When you have multiple sources cited in a paragraph, you are more likely to be synthesizing them (not always, but often
  • Read more about synthesis here.

The most interesting literature reviews are often written as arguments (again, as mentioned at the beginning of the page, this is discipline-specific and doesn’t work for all situations). Often, the literature review is where you can establish your research as filling a particular gap or as relevant in a particular way. You have some chance to do this in your introduction in an article, but the literature review section gives a more extended opportunity to establish the conversation in the way you would like your readers to see it. You can choose the intellectual lineage you would like to be part of and whose definitions matter most to your thinking (mostly humanities-specific, but this goes for sciences as well). In addressing these points, you argue for your place in the conversation, which tends to make the lit review more compelling than a simple reporting of other sources.

Libraries | Research Guides

Literature reviews, what is a literature review, learning more about how to do a literature review.

  • Planning the Review
  • The Research Question
  • Choosing Where to Search
  • Organizing the Review
  • Writing the Review

A literature review is a review and synthesis of existing research on a topic or research question. A literature review is meant to analyze the scholarly literature, make connections across writings and identify strengths, weaknesses, trends, and missing conversations. A literature review should address different aspects of a topic as it relates to your research question. A literature review goes beyond a description or summary of the literature you have read. 

  • Sage Research Methods Core Collection This link opens in a new window SAGE Research Methods supports research at all levels by providing material to guide users through every step of the research process. SAGE Research Methods is the ultimate methods library with more than 1000 books, reference works, journal articles, and instructional videos by world-leading academics from across the social sciences, including the largest collection of qualitative methods books available online from any scholarly publisher. – Publisher

Cover Art

  • Next: Planning the Review >>
  • Last Updated: Jan 17, 2024 10:05 AM
  • URL: https://libguides.northwestern.edu/literaturereviews
  • Resources Home 🏠
  • Try SciSpace Copilot
  • Search research papers
  • Add Copilot Extension
  • Try AI Detector
  • Try Paraphraser
  • Try Citation Generator
  • April Papers
  • June Papers
  • July Papers

SciSpace Resources

How To Write A Literature Review - A Complete Guide

Deeptanshu D

Table of Contents

A literature review is much more than just another section in your research paper. It forms the very foundation of your research. It is a formal piece of writing where you analyze the existing theoretical framework, principles, and assumptions and use that as a base to shape your approach to the research question.

Curating and drafting a solid literature review section not only lends more credibility to your research paper but also makes your research tighter and better focused. But, writing literature reviews is a difficult task. It requires extensive reading, plus you have to consider market trends and technological and political changes, which tend to change in the blink of an eye.

Now streamline your literature review process with the help of SciSpace Copilot. With this AI research assistant, you can efficiently synthesize and analyze a vast amount of information, identify key themes and trends, and uncover gaps in the existing research. Get real-time explanations, summaries, and answers to your questions for the paper you're reviewing, making navigating and understanding the complex literature landscape easier.

Perform Literature reviews using SciSpace Copilot

In this comprehensive guide, we will explore everything from the definition of a literature review, its appropriate length, various types of literature reviews, and how to write one.

What is a literature review?

A literature review is a collation of survey, research, critical evaluation, and assessment of the existing literature in a preferred domain.

Eminent researcher and academic Arlene Fink, in her book Conducting Research Literature Reviews , defines it as the following:

“A literature review surveys books, scholarly articles, and any other sources relevant to a particular issue, area of research, or theory, and by so doing, provides a description, summary, and critical evaluation of these works in relation to the research problem being investigated.

Literature reviews are designed to provide an overview of sources you have explored while researching a particular topic, and to demonstrate to your readers how your research fits within a larger field of study.”

Simply put, a literature review can be defined as a critical discussion of relevant pre-existing research around your research question and carving out a definitive place for your study in the existing body of knowledge. Literature reviews can be presented in multiple ways: a section of an article, the whole research paper itself, or a chapter of your thesis.

A literature review paper

A literature review does function as a summary of sources, but it also allows you to analyze further, interpret, and examine the stated theories, methods, viewpoints, and, of course, the gaps in the existing content.

As an author, you can discuss and interpret the research question and its various aspects and debate your adopted methods to support the claim.

What is the purpose of a literature review?

A literature review is meant to help your readers understand the relevance of your research question and where it fits within the existing body of knowledge. As a researcher, you should use it to set the context, build your argument, and establish the need for your study.

What is the importance of a literature review?

The literature review is a critical part of research papers because it helps you:

  • Gain an in-depth understanding of your research question and the surrounding area
  • Convey that you have a thorough understanding of your research area and are up-to-date with the latest changes and advancements
  • Establish how your research is connected or builds on the existing body of knowledge and how it could contribute to further research
  • Elaborate on the validity and suitability of your theoretical framework and research methodology
  • Identify and highlight gaps and shortcomings in the existing body of knowledge and how things need to change
  • Convey to readers how your study is different or how it contributes to the research area

How long should a literature review be?

Ideally, the literature review should take up 15%-40% of the total length of your manuscript. So, if you have a 10,000-word research paper, the minimum word count could be 1500.

Your literature review format depends heavily on the kind of manuscript you are writing — an entire chapter in case of doctoral theses, a part of the introductory section in a research article, to a full-fledged review article that examines the previously published research on a topic.

Another determining factor is the type of research you are doing. The literature review section tends to be longer for secondary research projects than primary research projects.

What are the different types of literature reviews?

All literature reviews are not the same. There are a variety of possible approaches that you can take. It all depends on the type of research you are pursuing.

Here are the different types of literature reviews:

Argumentative review

It is called an argumentative review when you carefully present literature that only supports or counters a specific argument or premise to establish a viewpoint.

Integrative review

It is a type of literature review focused on building a comprehensive understanding of a topic by combining available theoretical frameworks and empirical evidence.

Methodological review

This approach delves into the ''how'' and the ''what" of the research question —  you cannot look at the outcome in isolation; you should also review the methodology used.

Systematic review

This form consists of an overview of existing evidence pertinent to a clearly formulated research question, which uses pre-specified and standardized methods to identify and critically appraise relevant research and collect, report, and analyze data from the studies included in the review.

Meta-analysis review

Meta-analysis uses statistical methods to summarize the results of independent studies. By combining information from all relevant studies, meta-analysis can provide more precise estimates of the effects than those derived from the individual studies included within a review.

Historical review

Historical literature reviews focus on examining research throughout a period, often starting with the first time an issue, concept, theory, or phenomenon emerged in the literature, then tracing its evolution within the scholarship of a discipline. The purpose is to place research in a historical context to show familiarity with state-of-the-art developments and identify future research's likely directions.

Theoretical Review

This form aims to examine the corpus of theory accumulated regarding an issue, concept, theory, and phenomenon. The theoretical literature review helps to establish what theories exist, the relationships between them, the degree the existing approaches have been investigated, and to develop new hypotheses to be tested.

Scoping Review

The Scoping Review is often used at the beginning of an article, dissertation, or research proposal. It is conducted before the research to highlight gaps in the existing body of knowledge and explains why the project should be greenlit.

State-of-the-Art Review

The State-of-the-Art review is conducted periodically, focusing on the most recent research. It describes what is currently known, understood, or agreed upon regarding the research topic and highlights where there are still disagreements.

Can you use the first person in a literature review?

When writing literature reviews, you should avoid the usage of first-person pronouns. It means that instead of "I argue that" or "we argue that," the appropriate expression would be "this research paper argues that."

Do you need an abstract for a literature review?

Ideally, yes. It is always good to have a condensed summary that is self-contained and independent of the rest of your review. As for how to draft one, you can follow the same fundamental idea when preparing an abstract for a literature review. It should also include:

  • The research topic and your motivation behind selecting it
  • A one-sentence thesis statement
  • An explanation of the kinds of literature featured in the review
  • Summary of what you've learned
  • Conclusions you drew from the literature you reviewed
  • Potential implications and future scope for research

Here's an example of the abstract of a literature review

Abstract-of-a-literature-review

Is a literature review written in the past tense?

Yes, the literature review should ideally be written in the past tense. You should not use the present or future tense when writing one. The exceptions are when you have statements describing events that happened earlier than the literature you are reviewing or events that are currently occurring; then, you can use the past perfect or present perfect tenses.

How many sources for a literature review?

There are multiple approaches to deciding how many sources to include in a literature review section. The first approach would be to look level you are at as a researcher. For instance, a doctoral thesis might need 60+ sources. In contrast, you might only need to refer to 5-15 sources at the undergraduate level.

The second approach is based on the kind of literature review you are doing — whether it is merely a chapter of your paper or if it is a self-contained paper in itself. When it is just a chapter, sources should equal the total number of pages in your article's body. In the second scenario, you need at least three times as many sources as there are pages in your work.

Quick tips on how to write a literature review

To know how to write a literature review, you must clearly understand its impact and role in establishing your work as substantive research material.

You need to follow the below-mentioned steps, to write a literature review:

  • Outline the purpose behind the literature review
  • Search relevant literature
  • Examine and assess the relevant resources
  • Discover connections by drawing deep insights from the resources
  • Structure planning to write a good literature review

1. Outline and identify the purpose of  a literature review

As a first step on how to write a literature review, you must know what the research question or topic is and what shape you want your literature review to take. Ensure you understand the research topic inside out, or else seek clarifications. You must be able to the answer below questions before you start:

  • How many sources do I need to include?
  • What kind of sources should I analyze?
  • How much should I critically evaluate each source?
  • Should I summarize, synthesize or offer a critique of the sources?
  • Do I need to include any background information or definitions?

Additionally, you should know that the narrower your research topic is, the swifter it will be for you to restrict the number of sources to be analyzed.

2. Search relevant literature

Dig deeper into search engines to discover what has already been published around your chosen topic. Make sure you thoroughly go through appropriate reference sources like books, reports, journal articles, government docs, and web-based resources.

You must prepare a list of keywords and their different variations. You can start your search from any library’s catalog, provided you are an active member of that institution. The exact keywords can be extended to widen your research over other databases and academic search engines like:

  • Google Scholar
  • Microsoft Academic
  • Science.gov

Besides, it is not advisable to go through every resource word by word. Alternatively, what you can do is you can start by reading the abstract and then decide whether that source is relevant to your research or not.

Additionally, you must spend surplus time assessing the quality and relevance of resources. It would help if you tried preparing a list of citations to ensure that there lies no repetition of authors, publications, or articles in the literature review.

3. Examine and assess the sources

It is nearly impossible for you to go through every detail in the research article. So rather than trying to fetch every detail, you have to analyze and decide which research sources resemble closest and appear relevant to your chosen domain.

While analyzing the sources, you should look to find out answers to questions like:

  • What question or problem has the author been describing and debating?
  • What is the definition of critical aspects?
  • How well the theories, approach, and methodology have been explained?
  • Whether the research theory used some conventional or new innovative approach?
  • How relevant are the key findings of the work?
  • In what ways does it relate to other sources on the same topic?
  • What challenges does this research paper pose to the existing theory
  • What are the possible contributions or benefits it adds to the subject domain?

Be always mindful that you refer only to credible and authentic resources. It would be best if you always take references from different publications to validate your theory.

Always keep track of important information or data you can present in your literature review right from the beginning. It will help steer your path from any threats of plagiarism and also make it easier to curate an annotated bibliography or reference section.

4. Discover connections

At this stage, you must start deciding on the argument and structure of your literature review. To accomplish this, you must discover and identify the relations and connections between various resources while drafting your abstract.

A few aspects that you should be aware of while writing a literature review include:

  • Rise to prominence: Theories and methods that have gained reputation and supporters over time.
  • Constant scrutiny: Concepts or theories that repeatedly went under examination.
  • Contradictions and conflicts: Theories, both the supporting and the contradictory ones, for the research topic.
  • Knowledge gaps: What exactly does it fail to address, and how to bridge them with further research?
  • Influential resources: Significant research projects available that have been upheld as milestones or perhaps, something that can modify the current trends

Once you join the dots between various past research works, it will be easier for you to draw a conclusion and identify your contribution to the existing knowledge base.

5. Structure planning to write a good literature review

There exist different ways towards planning and executing the structure of a literature review. The format of a literature review varies and depends upon the length of the research.

Like any other research paper, the literature review format must contain three sections: introduction, body, and conclusion. The goals and objectives of the research question determine what goes inside these three sections.

Nevertheless, a good literature review can be structured according to the chronological, thematic, methodological, or theoretical framework approach.

Literature review samples

1. Standalone

Standalone-Literature-Review

2. As a section of a research paper

Literature-review-as-a-section-of-a-research-paper

How SciSpace Discover makes literature review a breeze?

SciSpace Discover is a one-stop solution to do an effective literature search and get barrier-free access to scientific knowledge. It is an excellent repository where you can find millions of only peer-reviewed articles and full-text PDF files. Here’s more on how you can use it:

Find the right information

Find-the-right-information-using-SciSpace

Find what you want quickly and easily with comprehensive search filters that let you narrow down papers according to PDF availability, year of publishing, document type, and affiliated institution. Moreover, you can sort the results based on the publishing date, citation count, and relevance.

Assess credibility of papers quickly

Assess-credibility-of-papers-quickly-using-SciSpace

When doing the literature review, it is critical to establish the quality of your sources. They form the foundation of your research. SciSpace Discover helps you assess the quality of a source by providing an overview of its references, citations, and performance metrics.

Get the complete picture in no time

SciSpace's-personalized-informtion-engine

SciSpace Discover’s personalized suggestion engine helps you stay on course and get the complete picture of the topic from one place. Every time you visit an article page, it provides you links to related papers. Besides that, it helps you understand what’s trending, who are the top authors, and who are the leading publishers on a topic.

Make referring sources super easy

Make-referring-pages-super-easy-with-SciSpace

To ensure you don't lose track of your sources, you must start noting down your references when doing the literature review. SciSpace Discover makes this step effortless. Click the 'cite' button on an article page, and you will receive preloaded citation text in multiple styles — all you've to do is copy-paste it into your manuscript.

Final tips on how to write a literature review

A massive chunk of time and effort is required to write a good literature review. But, if you go about it systematically, you'll be able to save a ton of time and build a solid foundation for your research.

We hope this guide has helped you answer several key questions you have about writing literature reviews.

Would you like to explore SciSpace Discover and kick off your literature search right away? You can get started here .

Frequently Asked Questions (FAQs)

1. how to start a literature review.

• What questions do you want to answer?

• What sources do you need to answer these questions?

• What information do these sources contain?

• How can you use this information to answer your questions?

2. What to include in a literature review?

• A brief background of the problem or issue

• What has previously been done to address the problem or issue

• A description of what you will do in your project

• How this study will contribute to research on the subject

3. Why literature review is important?

The literature review is an important part of any research project because it allows the writer to look at previous studies on a topic and determine existing gaps in the literature, as well as what has already been done. It will also help them to choose the most appropriate method for their own study.

4. How to cite a literature review in APA format?

To cite a literature review in APA style, you need to provide the author's name, the title of the article, and the year of publication. For example: Patel, A. B., & Stokes, G. S. (2012). The relationship between personality and intelligence: A meta-analysis of longitudinal research. Personality and Individual Differences, 53(1), 16-21

5. What are the components of a literature review?

• A brief introduction to the topic, including its background and context. The introduction should also include a rationale for why the study is being conducted and what it will accomplish.

• A description of the methodologies used in the study. This can include information about data collection methods, sample size, and statistical analyses.

• A presentation of the findings in an organized format that helps readers follow along with the author's conclusions.

6. What are common errors in writing literature review?

• Not spending enough time to critically evaluate the relevance of resources, observations and conclusions.

• Totally relying on secondary data while ignoring primary data.

• Letting your personal bias seep into your interpretation of existing literature.

• No detailed explanation of the procedure to discover and identify an appropriate literature review.

7. What are the 5 C's of writing literature review?

• Cite - the sources you utilized and referenced in your research.

• Compare - existing arguments, hypotheses, methodologies, and conclusions found in the knowledge base.

• Contrast - the arguments, topics, methodologies, approaches, and disputes that may be found in the literature.

• Critique - the literature and describe the ideas and opinions you find more convincing and why.

• Connect - the various studies you reviewed in your research.

8. How many sources should a literature review have?

When it is just a chapter, sources should equal the total number of pages in your article's body. if it is a self-contained paper in itself, you need at least three times as many sources as there are pages in your work.

9. Can literature review have diagrams?

• To represent an abstract idea or concept

• To explain the steps of a process or procedure

• To help readers understand the relationships between different concepts

10. How old should sources be in a literature review?

Sources for a literature review should be as current as possible or not older than ten years. The only exception to this rule is if you are reviewing a historical topic and need to use older sources.

11. What are the types of literature review?

• Argumentative review

• Integrative review

• Methodological review

• Systematic review

• Meta-analysis review

• Historical review

• Theoretical review

• Scoping review

• State-of-the-Art review

12. Is a literature review mandatory?

Yes. Literature review is a mandatory part of any research project. It is a critical step in the process that allows you to establish the scope of your research, and provide a background for the rest of your work.

But before you go,

  • Six Online Tools for Easy Literature Review
  • Evaluating literature review: systematic vs. scoping reviews
  • Systematic Approaches to a Successful Literature Review
  • Writing Integrative Literature Reviews: Guidelines and Examples

You might also like

Consensus GPT vs. SciSpace GPT: Choose the Best GPT for Research

Consensus GPT vs. SciSpace GPT: Choose the Best GPT for Research

Sumalatha G

Literature Review and Theoretical Framework: Understanding the Differences

Nikhil Seethi

Types of Essays in Academic Writing

Literature reviews

What this guide covers, what is a literature review, literature review resources, types of literature reviews, what is the difference between a literature review and a systematic review, related information and guides, further help.

  • Conducting your search
  • Store and organise the literature
  • Evaluate and critique the literature
  • Different subject areas
  • Find literature reviews

Reusing content from this guide

what are the characteristics of a literature review

Attribute our work under a Creative Commons Attribution-NonCommercial 4.0 International License.

1. Select a topic; 2. Search for literature; 3. Survey the literature; 4. Appraise the literature; 5. Write the review

The literature review process involves a number of steps.

This guide focuses on:

  • evaluating.

A literature review is a survey and critical analysis of what has been written on a particular topic, theory, question or method.

"In writing the literature review, the purpose is to explore what knowledge and ideas have been established on a topic, what approaches and viewpoints have been adopted, and what are their strengths and weaknesses."

Source: "Focus and frame". (2008). In Eriksson, P. & Kovalainen, A. Introducing Qualitative Methods: Qualitative methods in business research (pp. 44) . London: SAGE Publications Ltd. doi: 10.4135/9780857028044.

Get an overview on doing a literature review:

  • Sage research methods online - Literature review methods map Information on the literature review methodology with links to further resources - the Project Planner, books, articles, videos and more.
  • Ten simple rules for writing a literature review Gives 10 tips on how to approach and carry out a literature review. By Pautasso M (2013) Ten Simple Rules for Writing a Literature Review. PLoS Comput Biol9(7): e1003149.
  • The literature review. In: Doing your undergraduate program This chapter looks at the purpose of literature reviews, how it is done, setting the boundaries of your search and more.

Cover Art

  • More books on literature reviews A selection of literature review books available via UQ Library Search.

The type of literature review you do will depend on a variety of factors:

  • Your discipline
  • The purpose - undergraduate assessment, PHD thesis, journal article?
  • Your lecturer or supervisor's requirements

Always follow the guidelines outlined by your lecturer or supervisor or consult the instructions for authors (for journal articles), when conducting your literature review.

  • is an overview of the significant literature on a topic
  • typically includes a critical analysis of each work included
  • demonstrates the reviewers knowledge of the topic
  • is a list of citations of research sources (books, journal articles, websites etc) on a topic
  • includes a brief summary and analysis or evaluation of each citation = the annotation
  • a critical assessment of all research studies on a particular research question
  • has specific criteria for collecting and evaluating the literature
  • includes a synthesis of the findings of the included studies
  • This method developed by Griffith University's School of Environment bridges the gap between traditional narrative review methods and meta-analyses to enable students to produce results that are reliable, quantifiable and reproducible.

The requirements of narrative literature reviews are usually quite different than systematic reviews . However, you may be required to adopt some of the characteristics of a systematic approach when doing your literature review. Check the guidelines or criteria that have been set by your supervisor so you know what is expected of you.

Characteristics of reviews

  • Meeting the review family: Exploring review types and associated information retrieval requirements This article defines different review types and discusses appropriate search methods for each type.
  • Writing literature reviews - Student Support Student Support provides information on how to write effective literature reviews.
  • Writing skills Learn strategies for good writing from the Graduate School.
  • Systematic reviews An overview of systematic reviews and resources to support producing one.
  • Subject guides See recommended resources in different subject areas.
  • Grey literature Find literature that is not available in traditional channels of publishing and distribution.
  • How to find guides Techniques and resources to find specific information formats.

Contact the Librarian team .

Phone: + 617 334 64312 during opening hours

Email: [email protected]

  • Next: Conducting your search >>
  • Last Updated: Dec 15, 2023 12:09 PM
  • URL: https://guides.library.uq.edu.au/research-techniques/literature-reviews

University of Texas

  • University of Texas Libraries

Literature Reviews

  • What is a literature review?
  • Steps in the Literature Review Process
  • Define your research question
  • Determine inclusion and exclusion criteria
  • Choose databases and search
  • Review Results
  • Synthesize Results
  • Analyze Results
  • Librarian Support

What is a Literature Review?

A literature or narrative review is a comprehensive review and analysis of the published literature on a specific topic or research question. The literature that is reviewed contains: books, articles, academic articles, conference proceedings, association papers, and dissertations. It contains the most pertinent studies and points to important past and current research and practices. It provides background and context, and shows how your research will contribute to the field. 

A literature review should: 

  • Provide a comprehensive and updated review of the literature;
  • Explain why this review has taken place;
  • Articulate a position or hypothesis;
  • Acknowledge and account for conflicting and corroborating points of view

From  S age Research Methods

Purpose of a Literature Review

A literature review can be written as an introduction to a study to:

  • Demonstrate how a study fills a gap in research
  • Compare a study with other research that's been done

Or it can be a separate work (a research article on its own) which:

  • Organizes or describes a topic
  • Describes variables within a particular issue/problem

Limitations of a Literature Review

Some of the limitations of a literature review are:

  • It's a snapshot in time. Unlike other reviews, this one has beginning, a middle and an end. There may be future developments that could make your work less relevant.
  • It may be too focused. Some niche studies may miss the bigger picture.
  • It can be difficult to be comprehensive. There is no way to make sure all the literature on a topic was considered.
  • It is easy to be biased if you stick to top tier journals. There may be other places where people are publishing exemplary research. Look to open access publications and conferences to reflect a more inclusive collection. Also, make sure to include opposing views (and not just supporting evidence).

Source: Grant, Maria J., and Andrew Booth. “A Typology of Reviews: An Analysis of 14 Review Types and Associated Methodologies.” Health Information & Libraries Journal, vol. 26, no. 2, June 2009, pp. 91–108. Wiley Online Library, doi:10.1111/j.1471-1842.2009.00848.x.

Meryl Brodsky : Communication and Information Studies

Hannah Chapman Tripp : Biology, Neuroscience

Carolyn Cunningham : Human Development & Family Sciences, Psychology, Sociology

Larayne Dallas : Engineering

Janelle Hedstrom : Special Education, Curriculum & Instruction, Ed Leadership & Policy ​

Susan Macicak : Linguistics

Imelda Vetter : Dell Medical School

For help in other subject areas, please see the guide to library specialists by subject .

Periodically, UT Libraries runs a workshop covering the basics and library support for literature reviews. While we try to offer these once per academic year, we find providing the recording to be helpful to community members who have missed the session. Following is the most recent recording of the workshop, Conducting a Literature Review. To view the recording, a UT login is required.

  • October 26, 2022 recording
  • Last Updated: Oct 26, 2022 2:49 PM
  • URL: https://guides.lib.utexas.edu/literaturereviews

Creative Commons License

Have a language expert improve your writing

Run a free plagiarism check in 10 minutes, automatically generate references for free.

  • Knowledge Base
  • Dissertation
  • What is a Literature Review? | Guide, Template, & Examples

What is a Literature Review? | Guide, Template, & Examples

Published on 22 February 2022 by Shona McCombes . Revised on 7 June 2022.

What is a literature review? A literature review is a survey of scholarly sources on a specific topic. It provides an overview of current knowledge, allowing you to identify relevant theories, methods, and gaps in the existing research.

There are five key steps to writing a literature review:

  • Search for relevant literature
  • Evaluate sources
  • Identify themes, debates and gaps
  • Outline the structure
  • Write your literature review

A good literature review doesn’t just summarise sources – it analyses, synthesises, and critically evaluates to give a clear picture of the state of knowledge on the subject.

Instantly correct all language mistakes in your text

Be assured that you'll submit flawless writing. Upload your document to correct all your mistakes.

upload-your-document-ai-proofreader

Table of contents

Why write a literature review, examples of literature reviews, step 1: search for relevant literature, step 2: evaluate and select sources, step 3: identify themes, debates and gaps, step 4: outline your literature review’s structure, step 5: write your literature review, frequently asked questions about literature reviews, introduction.

  • Quick Run-through
  • Step 1 & 2

When you write a dissertation or thesis, you will have to conduct a literature review to situate your research within existing knowledge. The literature review gives you a chance to:

  • Demonstrate your familiarity with the topic and scholarly context
  • Develop a theoretical framework and methodology for your research
  • Position yourself in relation to other researchers and theorists
  • Show how your dissertation addresses a gap or contributes to a debate

You might also have to write a literature review as a stand-alone assignment. In this case, the purpose is to evaluate the current state of research and demonstrate your knowledge of scholarly debates around a topic.

The content will look slightly different in each case, but the process of conducting a literature review follows the same steps. We’ve written a step-by-step guide that you can follow below.

Literature review guide

The only proofreading tool specialized in correcting academic writing

The academic proofreading tool has been trained on 1000s of academic texts and by native English editors. Making it the most accurate and reliable proofreading tool for students.

what are the characteristics of a literature review

Correct my document today

Writing literature reviews can be quite challenging! A good starting point could be to look at some examples, depending on what kind of literature review you’d like to write.

  • Example literature review #1: “Why Do People Migrate? A Review of the Theoretical Literature” ( Theoretical literature review about the development of economic migration theory from the 1950s to today.)
  • Example literature review #2: “Literature review as a research methodology: An overview and guidelines” ( Methodological literature review about interdisciplinary knowledge acquisition and production.)
  • Example literature review #3: “The Use of Technology in English Language Learning: A Literature Review” ( Thematic literature review about the effects of technology on language acquisition.)
  • Example literature review #4: “Learners’ Listening Comprehension Difficulties in English Language Learning: A Literature Review” ( Chronological literature review about how the concept of listening skills has changed over time.)

You can also check out our templates with literature review examples and sample outlines at the links below.

Download Word doc Download Google doc

Before you begin searching for literature, you need a clearly defined topic .

If you are writing the literature review section of a dissertation or research paper, you will search for literature related to your research objectives and questions .

If you are writing a literature review as a stand-alone assignment, you will have to choose a focus and develop a central question to direct your search. Unlike a dissertation research question, this question has to be answerable without collecting original data. You should be able to answer it based only on a review of existing publications.

Make a list of keywords

Start by creating a list of keywords related to your research topic. Include each of the key concepts or variables you’re interested in, and list any synonyms and related terms. You can add to this list if you discover new keywords in the process of your literature search.

  • Social media, Facebook, Instagram, Twitter, Snapchat, TikTok
  • Body image, self-perception, self-esteem, mental health
  • Generation Z, teenagers, adolescents, youth

Search for relevant sources

Use your keywords to begin searching for sources. Some databases to search for journals and articles include:

  • Your university’s library catalogue
  • Google Scholar
  • Project Muse (humanities and social sciences)
  • Medline (life sciences and biomedicine)
  • EconLit (economics)
  • Inspec (physics, engineering and computer science)

You can use boolean operators to help narrow down your search:

Read the abstract to find out whether an article is relevant to your question. When you find a useful book or article, you can check the bibliography to find other relevant sources.

To identify the most important publications on your topic, take note of recurring citations. If the same authors, books or articles keep appearing in your reading, make sure to seek them out.

You probably won’t be able to read absolutely everything that has been written on the topic – you’ll have to evaluate which sources are most relevant to your questions.

For each publication, ask yourself:

  • What question or problem is the author addressing?
  • What are the key concepts and how are they defined?
  • What are the key theories, models and methods? Does the research use established frameworks or take an innovative approach?
  • What are the results and conclusions of the study?
  • How does the publication relate to other literature in the field? Does it confirm, add to, or challenge established knowledge?
  • How does the publication contribute to your understanding of the topic? What are its key insights and arguments?
  • What are the strengths and weaknesses of the research?

Make sure the sources you use are credible, and make sure you read any landmark studies and major theories in your field of research.

You can find out how many times an article has been cited on Google Scholar – a high citation count means the article has been influential in the field, and should certainly be included in your literature review.

The scope of your review will depend on your topic and discipline: in the sciences you usually only review recent literature, but in the humanities you might take a long historical perspective (for example, to trace how a concept has changed in meaning over time).

Remember that you can use our template to summarise and evaluate sources you’re thinking about using!

Take notes and cite your sources

As you read, you should also begin the writing process. Take notes that you can later incorporate into the text of your literature review.

It’s important to keep track of your sources with references to avoid plagiarism . It can be helpful to make an annotated bibliography, where you compile full reference information and write a paragraph of summary and analysis for each source. This helps you remember what you read and saves time later in the process.

You can use our free APA Reference Generator for quick, correct, consistent citations.

To begin organising your literature review’s argument and structure, you need to understand the connections and relationships between the sources you’ve read. Based on your reading and notes, you can look for:

  • Trends and patterns (in theory, method or results): do certain approaches become more or less popular over time?
  • Themes: what questions or concepts recur across the literature?
  • Debates, conflicts and contradictions: where do sources disagree?
  • Pivotal publications: are there any influential theories or studies that changed the direction of the field?
  • Gaps: what is missing from the literature? Are there weaknesses that need to be addressed?

This step will help you work out the structure of your literature review and (if applicable) show how your own research will contribute to existing knowledge.

  • Most research has focused on young women.
  • There is an increasing interest in the visual aspects of social media.
  • But there is still a lack of robust research on highly-visual platforms like Instagram and Snapchat – this is a gap that you could address in your own research.

There are various approaches to organising the body of a literature review. You should have a rough idea of your strategy before you start writing.

Depending on the length of your literature review, you can combine several of these strategies (for example, your overall structure might be thematic, but each theme is discussed chronologically).

Chronological

The simplest approach is to trace the development of the topic over time. However, if you choose this strategy, be careful to avoid simply listing and summarising sources in order.

Try to analyse patterns, turning points and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred.

If you have found some recurring central themes, you can organise your literature review into subsections that address different aspects of the topic.

For example, if you are reviewing literature about inequalities in migrant health outcomes, key themes might include healthcare policy, language barriers, cultural attitudes, legal status, and economic access.

Methodological

If you draw your sources from different disciplines or fields that use a variety of research methods , you might want to compare the results and conclusions that emerge from different approaches. For example:

  • Look at what results have emerged in qualitative versus quantitative research
  • Discuss how the topic has been approached by empirical versus theoretical scholarship
  • Divide the literature into sociological, historical, and cultural sources

Theoretical

A literature review is often the foundation for a theoretical framework . You can use it to discuss various theories, models, and definitions of key concepts.

You might argue for the relevance of a specific theoretical approach, or combine various theoretical concepts to create a framework for your research.

Like any other academic text, your literature review should have an introduction , a main body, and a conclusion . What you include in each depends on the objective of your literature review.

The introduction should clearly establish the focus and purpose of the literature review.

If you are writing the literature review as part of your dissertation or thesis, reiterate your central problem or research question and give a brief summary of the scholarly context. You can emphasise the timeliness of the topic (“many recent studies have focused on the problem of x”) or highlight a gap in the literature (“while there has been much research on x, few researchers have taken y into consideration”).

Depending on the length of your literature review, you might want to divide the body into subsections. You can use a subheading for each theme, time period, or methodological approach.

As you write, make sure to follow these tips:

  • Summarise and synthesise: give an overview of the main points of each source and combine them into a coherent whole.
  • Analyse and interpret: don’t just paraphrase other researchers – add your own interpretations, discussing the significance of findings in relation to the literature as a whole.
  • Critically evaluate: mention the strengths and weaknesses of your sources.
  • Write in well-structured paragraphs: use transitions and topic sentences to draw connections, comparisons and contrasts.

In the conclusion, you should summarise the key findings you have taken from the literature and emphasise their significance.

If the literature review is part of your dissertation or thesis, reiterate how your research addresses gaps and contributes new knowledge, or discuss how you have drawn on existing theories and methods to build a framework for your research. This can lead directly into your methodology section.

A literature review is a survey of scholarly sources (such as books, journal articles, and theses) related to a specific topic or research question .

It is often written as part of a dissertation , thesis, research paper , or proposal .

There are several reasons to conduct a literature review at the beginning of a research project:

  • To familiarise yourself with the current state of knowledge on your topic
  • To ensure that you’re not just repeating what others have already done
  • To identify gaps in knowledge and unresolved problems that your research can address
  • To develop your theoretical framework and methodology
  • To provide an overview of the key findings and debates on the topic

Writing the literature review shows your reader how your work relates to existing research and what new insights it will contribute.

The literature review usually comes near the beginning of your  dissertation . After the introduction , it grounds your research in a scholarly field and leads directly to your theoretical framework or methodology .

Cite this Scribbr article

If you want to cite this source, you can copy and paste the citation or click the ‘Cite this Scribbr article’ button to automatically add the citation to our free Reference Generator.

McCombes, S. (2022, June 07). What is a Literature Review? | Guide, Template, & Examples. Scribbr. Retrieved 20 March 2024, from https://www.scribbr.co.uk/thesis-dissertation/literature-review/

Is this article helpful?

Shona McCombes

Shona McCombes

Other students also liked, how to write a dissertation proposal | a step-by-step guide, what is a theoretical framework | a step-by-step guide, what is a research methodology | steps & tips.

  • USC Libraries
  • Research Guides

Organizing Your Social Sciences Research Paper

  • 5. The Literature Review
  • Purpose of Guide
  • Design Flaws to Avoid
  • Independent and Dependent Variables
  • Glossary of Research Terms
  • Reading Research Effectively
  • Narrowing a Topic Idea
  • Broadening a Topic Idea
  • Extending the Timeliness of a Topic Idea
  • Academic Writing Style
  • Choosing a Title
  • Making an Outline
  • Paragraph Development
  • Research Process Video Series
  • Executive Summary
  • The C.A.R.S. Model
  • Background Information
  • The Research Problem/Question
  • Theoretical Framework
  • Citation Tracking
  • Content Alert Services
  • Evaluating Sources
  • Primary Sources
  • Secondary Sources
  • Tiertiary Sources
  • Scholarly vs. Popular Publications
  • Qualitative Methods
  • Quantitative Methods
  • Insiderness
  • Using Non-Textual Elements
  • Limitations of the Study
  • Common Grammar Mistakes
  • Writing Concisely
  • Avoiding Plagiarism
  • Footnotes or Endnotes?
  • Further Readings
  • Generative AI and Writing
  • USC Libraries Tutorials and Other Guides
  • Bibliography

A literature review surveys prior research published in books, scholarly articles, and any other sources relevant to a particular issue, area of research, or theory, and by so doing, provides a description, summary, and critical evaluation of these works in relation to the research problem being investigated. Literature reviews are designed to provide an overview of sources you have used in researching a particular topic and to demonstrate to your readers how your research fits within existing scholarship about the topic.

Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper . Fourth edition. Thousand Oaks, CA: SAGE, 2014.

Importance of a Good Literature Review

A literature review may consist of simply a summary of key sources, but in the social sciences, a literature review usually has an organizational pattern and combines both summary and synthesis, often within specific conceptual categories . A summary is a recap of the important information of the source, but a synthesis is a re-organization, or a reshuffling, of that information in a way that informs how you are planning to investigate a research problem. The analytical features of a literature review might:

  • Give a new interpretation of old material or combine new with old interpretations,
  • Trace the intellectual progression of the field, including major debates,
  • Depending on the situation, evaluate the sources and advise the reader on the most pertinent or relevant research, or
  • Usually in the conclusion of a literature review, identify where gaps exist in how a problem has been researched to date.

Given this, the purpose of a literature review is to:

  • Place each work in the context of its contribution to understanding the research problem being studied.
  • Describe the relationship of each work to the others under consideration.
  • Identify new ways to interpret prior research.
  • Reveal any gaps that exist in the literature.
  • Resolve conflicts amongst seemingly contradictory previous studies.
  • Identify areas of prior scholarship to prevent duplication of effort.
  • Point the way in fulfilling a need for additional research.
  • Locate your own research within the context of existing literature [very important].

Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper. 2nd ed. Thousand Oaks, CA: Sage, 2005; Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1998; Jesson, Jill. Doing Your Literature Review: Traditional and Systematic Techniques . Los Angeles, CA: SAGE, 2011; Knopf, Jeffrey W. "Doing a Literature Review." PS: Political Science and Politics 39 (January 2006): 127-132; Ridley, Diana. The Literature Review: A Step-by-Step Guide for Students . 2nd ed. Los Angeles, CA: SAGE, 2012.

Types of Literature Reviews

It is important to think of knowledge in a given field as consisting of three layers. First, there are the primary studies that researchers conduct and publish. Second are the reviews of those studies that summarize and offer new interpretations built from and often extending beyond the primary studies. Third, there are the perceptions, conclusions, opinion, and interpretations that are shared informally among scholars that become part of the body of epistemological traditions within the field.

In composing a literature review, it is important to note that it is often this third layer of knowledge that is cited as "true" even though it often has only a loose relationship to the primary studies and secondary literature reviews. Given this, while literature reviews are designed to provide an overview and synthesis of pertinent sources you have explored, there are a number of approaches you could adopt depending upon the type of analysis underpinning your study.

Argumentative Review This form examines literature selectively in order to support or refute an argument, deeply embedded assumption, or philosophical problem already established in the literature. The purpose is to develop a body of literature that establishes a contrarian viewpoint. Given the value-laden nature of some social science research [e.g., educational reform; immigration control], argumentative approaches to analyzing the literature can be a legitimate and important form of discourse. However, note that they can also introduce problems of bias when they are used to make summary claims of the sort found in systematic reviews [see below].

Integrative Review Considered a form of research that reviews, critiques, and synthesizes representative literature on a topic in an integrated way such that new frameworks and perspectives on the topic are generated. The body of literature includes all studies that address related or identical hypotheses or research problems. A well-done integrative review meets the same standards as primary research in regard to clarity, rigor, and replication. This is the most common form of review in the social sciences.

Historical Review Few things rest in isolation from historical precedent. Historical literature reviews focus on examining research throughout a period of time, often starting with the first time an issue, concept, theory, phenomena emerged in the literature, then tracing its evolution within the scholarship of a discipline. The purpose is to place research in a historical context to show familiarity with state-of-the-art developments and to identify the likely directions for future research.

Methodological Review A review does not always focus on what someone said [findings], but how they came about saying what they say [method of analysis]. Reviewing methods of analysis provides a framework of understanding at different levels [i.e. those of theory, substantive fields, research approaches, and data collection and analysis techniques], how researchers draw upon a wide variety of knowledge ranging from the conceptual level to practical documents for use in fieldwork in the areas of ontological and epistemological consideration, quantitative and qualitative integration, sampling, interviewing, data collection, and data analysis. This approach helps highlight ethical issues which you should be aware of and consider as you go through your own study.

Systematic Review This form consists of an overview of existing evidence pertinent to a clearly formulated research question, which uses pre-specified and standardized methods to identify and critically appraise relevant research, and to collect, report, and analyze data from the studies that are included in the review. The goal is to deliberately document, critically evaluate, and summarize scientifically all of the research about a clearly defined research problem . Typically it focuses on a very specific empirical question, often posed in a cause-and-effect form, such as "To what extent does A contribute to B?" This type of literature review is primarily applied to examining prior research studies in clinical medicine and allied health fields, but it is increasingly being used in the social sciences.

Theoretical Review The purpose of this form is to examine the corpus of theory that has accumulated in regard to an issue, concept, theory, phenomena. The theoretical literature review helps to establish what theories already exist, the relationships between them, to what degree the existing theories have been investigated, and to develop new hypotheses to be tested. Often this form is used to help establish a lack of appropriate theories or reveal that current theories are inadequate for explaining new or emerging research problems. The unit of analysis can focus on a theoretical concept or a whole theory or framework.

NOTE : Most often the literature review will incorporate some combination of types. For example, a review that examines literature supporting or refuting an argument, assumption, or philosophical problem related to the research problem will also need to include writing supported by sources that establish the history of these arguments in the literature.

Baumeister, Roy F. and Mark R. Leary. "Writing Narrative Literature Reviews."  Review of General Psychology 1 (September 1997): 311-320; Mark R. Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper . 2nd ed. Thousand Oaks, CA: Sage, 2005; Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1998; Kennedy, Mary M. "Defining a Literature." Educational Researcher 36 (April 2007): 139-147; Petticrew, Mark and Helen Roberts. Systematic Reviews in the Social Sciences: A Practical Guide . Malden, MA: Blackwell Publishers, 2006; Torracro, Richard. "Writing Integrative Literature Reviews: Guidelines and Examples." Human Resource Development Review 4 (September 2005): 356-367; Rocco, Tonette S. and Maria S. Plakhotnik. "Literature Reviews, Conceptual Frameworks, and Theoretical Frameworks: Terms, Functions, and Distinctions." Human Ressource Development Review 8 (March 2008): 120-130; Sutton, Anthea. Systematic Approaches to a Successful Literature Review . Los Angeles, CA: Sage Publications, 2016.

Structure and Writing Style

I.  Thinking About Your Literature Review

The structure of a literature review should include the following in support of understanding the research problem :

  • An overview of the subject, issue, or theory under consideration, along with the objectives of the literature review,
  • Division of works under review into themes or categories [e.g. works that support a particular position, those against, and those offering alternative approaches entirely],
  • An explanation of how each work is similar to and how it varies from the others,
  • Conclusions as to which pieces are best considered in their argument, are most convincing of their opinions, and make the greatest contribution to the understanding and development of their area of research.

The critical evaluation of each work should consider :

  • Provenance -- what are the author's credentials? Are the author's arguments supported by evidence [e.g. primary historical material, case studies, narratives, statistics, recent scientific findings]?
  • Methodology -- were the techniques used to identify, gather, and analyze the data appropriate to addressing the research problem? Was the sample size appropriate? Were the results effectively interpreted and reported?
  • Objectivity -- is the author's perspective even-handed or prejudicial? Is contrary data considered or is certain pertinent information ignored to prove the author's point?
  • Persuasiveness -- which of the author's theses are most convincing or least convincing?
  • Validity -- are the author's arguments and conclusions convincing? Does the work ultimately contribute in any significant way to an understanding of the subject?

II.  Development of the Literature Review

Four Basic Stages of Writing 1.  Problem formulation -- which topic or field is being examined and what are its component issues? 2.  Literature search -- finding materials relevant to the subject being explored. 3.  Data evaluation -- determining which literature makes a significant contribution to the understanding of the topic. 4.  Analysis and interpretation -- discussing the findings and conclusions of pertinent literature.

Consider the following issues before writing the literature review: Clarify If your assignment is not specific about what form your literature review should take, seek clarification from your professor by asking these questions: 1.  Roughly how many sources would be appropriate to include? 2.  What types of sources should I review (books, journal articles, websites; scholarly versus popular sources)? 3.  Should I summarize, synthesize, or critique sources by discussing a common theme or issue? 4.  Should I evaluate the sources in any way beyond evaluating how they relate to understanding the research problem? 5.  Should I provide subheadings and other background information, such as definitions and/or a history? Find Models Use the exercise of reviewing the literature to examine how authors in your discipline or area of interest have composed their literature review sections. Read them to get a sense of the types of themes you might want to look for in your own research or to identify ways to organize your final review. The bibliography or reference section of sources you've already read, such as required readings in the course syllabus, are also excellent entry points into your own research. Narrow the Topic The narrower your topic, the easier it will be to limit the number of sources you need to read in order to obtain a good survey of relevant resources. Your professor will probably not expect you to read everything that's available about the topic, but you'll make the act of reviewing easier if you first limit scope of the research problem. A good strategy is to begin by searching the USC Libraries Catalog for recent books about the topic and review the table of contents for chapters that focuses on specific issues. You can also review the indexes of books to find references to specific issues that can serve as the focus of your research. For example, a book surveying the history of the Israeli-Palestinian conflict may include a chapter on the role Egypt has played in mediating the conflict, or look in the index for the pages where Egypt is mentioned in the text. Consider Whether Your Sources are Current Some disciplines require that you use information that is as current as possible. This is particularly true in disciplines in medicine and the sciences where research conducted becomes obsolete very quickly as new discoveries are made. However, when writing a review in the social sciences, a survey of the history of the literature may be required. In other words, a complete understanding the research problem requires you to deliberately examine how knowledge and perspectives have changed over time. Sort through other current bibliographies or literature reviews in the field to get a sense of what your discipline expects. You can also use this method to explore what is considered by scholars to be a "hot topic" and what is not.

III.  Ways to Organize Your Literature Review

Chronology of Events If your review follows the chronological method, you could write about the materials according to when they were published. This approach should only be followed if a clear path of research building on previous research can be identified and that these trends follow a clear chronological order of development. For example, a literature review that focuses on continuing research about the emergence of German economic power after the fall of the Soviet Union. By Publication Order your sources by publication chronology, then, only if the order demonstrates a more important trend. For instance, you could order a review of literature on environmental studies of brown fields if the progression revealed, for example, a change in the soil collection practices of the researchers who wrote and/or conducted the studies. Thematic [“conceptual categories”] A thematic literature review is the most common approach to summarizing prior research in the social and behavioral sciences. Thematic reviews are organized around a topic or issue, rather than the progression of time, although the progression of time may still be incorporated into a thematic review. For example, a review of the Internet’s impact on American presidential politics could focus on the development of online political satire. While the study focuses on one topic, the Internet’s impact on American presidential politics, it would still be organized chronologically reflecting technological developments in media. The difference in this example between a "chronological" and a "thematic" approach is what is emphasized the most: themes related to the role of the Internet in presidential politics. Note that more authentic thematic reviews tend to break away from chronological order. A review organized in this manner would shift between time periods within each section according to the point being made. Methodological A methodological approach focuses on the methods utilized by the researcher. For the Internet in American presidential politics project, one methodological approach would be to look at cultural differences between the portrayal of American presidents on American, British, and French websites. Or the review might focus on the fundraising impact of the Internet on a particular political party. A methodological scope will influence either the types of documents in the review or the way in which these documents are discussed.

Other Sections of Your Literature Review Once you've decided on the organizational method for your literature review, the sections you need to include in the paper should be easy to figure out because they arise from your organizational strategy. In other words, a chronological review would have subsections for each vital time period; a thematic review would have subtopics based upon factors that relate to the theme or issue. However, sometimes you may need to add additional sections that are necessary for your study, but do not fit in the organizational strategy of the body. What other sections you include in the body is up to you. However, only include what is necessary for the reader to locate your study within the larger scholarship about the research problem.

Here are examples of other sections, usually in the form of a single paragraph, you may need to include depending on the type of review you write:

  • Current Situation : Information necessary to understand the current topic or focus of the literature review.
  • Sources Used : Describes the methods and resources [e.g., databases] you used to identify the literature you reviewed.
  • History : The chronological progression of the field, the research literature, or an idea that is necessary to understand the literature review, if the body of the literature review is not already a chronology.
  • Selection Methods : Criteria you used to select (and perhaps exclude) sources in your literature review. For instance, you might explain that your review includes only peer-reviewed [i.e., scholarly] sources.
  • Standards : Description of the way in which you present your information.
  • Questions for Further Research : What questions about the field has the review sparked? How will you further your research as a result of the review?

IV.  Writing Your Literature Review

Once you've settled on how to organize your literature review, you're ready to write each section. When writing your review, keep in mind these issues.

Use Evidence A literature review section is, in this sense, just like any other academic research paper. Your interpretation of the available sources must be backed up with evidence [citations] that demonstrates that what you are saying is valid. Be Selective Select only the most important points in each source to highlight in the review. The type of information you choose to mention should relate directly to the research problem, whether it is thematic, methodological, or chronological. Related items that provide additional information, but that are not key to understanding the research problem, can be included in a list of further readings . Use Quotes Sparingly Some short quotes are appropriate if you want to emphasize a point, or if what an author stated cannot be easily paraphrased. Sometimes you may need to quote certain terminology that was coined by the author, is not common knowledge, or taken directly from the study. Do not use extensive quotes as a substitute for using your own words in reviewing the literature. Summarize and Synthesize Remember to summarize and synthesize your sources within each thematic paragraph as well as throughout the review. Recapitulate important features of a research study, but then synthesize it by rephrasing the study's significance and relating it to your own work and the work of others. Keep Your Own Voice While the literature review presents others' ideas, your voice [the writer's] should remain front and center. For example, weave references to other sources into what you are writing but maintain your own voice by starting and ending the paragraph with your own ideas and wording. Use Caution When Paraphrasing When paraphrasing a source that is not your own, be sure to represent the author's information or opinions accurately and in your own words. Even when paraphrasing an author’s work, you still must provide a citation to that work.

V.  Common Mistakes to Avoid

These are the most common mistakes made in reviewing social science research literature.

  • Sources in your literature review do not clearly relate to the research problem;
  • You do not take sufficient time to define and identify the most relevant sources to use in the literature review related to the research problem;
  • Relies exclusively on secondary analytical sources rather than including relevant primary research studies or data;
  • Uncritically accepts another researcher's findings and interpretations as valid, rather than examining critically all aspects of the research design and analysis;
  • Does not describe the search procedures that were used in identifying the literature to review;
  • Reports isolated statistical results rather than synthesizing them in chi-squared or meta-analytic methods; and,
  • Only includes research that validates assumptions and does not consider contrary findings and alternative interpretations found in the literature.

Cook, Kathleen E. and Elise Murowchick. “Do Literature Review Skills Transfer from One Course to Another?” Psychology Learning and Teaching 13 (March 2014): 3-11; Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper . 2nd ed. Thousand Oaks, CA: Sage, 2005; Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1998; Jesson, Jill. Doing Your Literature Review: Traditional and Systematic Techniques . London: SAGE, 2011; Literature Review Handout. Online Writing Center. Liberty University; Literature Reviews. The Writing Center. University of North Carolina; Onwuegbuzie, Anthony J. and Rebecca Frels. Seven Steps to a Comprehensive Literature Review: A Multimodal and Cultural Approach . Los Angeles, CA: SAGE, 2016; Ridley, Diana. The Literature Review: A Step-by-Step Guide for Students . 2nd ed. Los Angeles, CA: SAGE, 2012; Randolph, Justus J. “A Guide to Writing the Dissertation Literature Review." Practical Assessment, Research, and Evaluation. vol. 14, June 2009; Sutton, Anthea. Systematic Approaches to a Successful Literature Review . Los Angeles, CA: Sage Publications, 2016; Taylor, Dena. The Literature Review: A Few Tips On Conducting It. University College Writing Centre. University of Toronto; Writing a Literature Review. Academic Skills Centre. University of Canberra.

Writing Tip

Break Out of Your Disciplinary Box!

Thinking interdisciplinarily about a research problem can be a rewarding exercise in applying new ideas, theories, or concepts to an old problem. For example, what might cultural anthropologists say about the continuing conflict in the Middle East? In what ways might geographers view the need for better distribution of social service agencies in large cities than how social workers might study the issue? You don’t want to substitute a thorough review of core research literature in your discipline for studies conducted in other fields of study. However, particularly in the social sciences, thinking about research problems from multiple vectors is a key strategy for finding new solutions to a problem or gaining a new perspective. Consult with a librarian about identifying research databases in other disciplines; almost every field of study has at least one comprehensive database devoted to indexing its research literature.

Frodeman, Robert. The Oxford Handbook of Interdisciplinarity . New York: Oxford University Press, 2010.

Another Writing Tip

Don't Just Review for Content!

While conducting a review of the literature, maximize the time you devote to writing this part of your paper by thinking broadly about what you should be looking for and evaluating. Review not just what scholars are saying, but how are they saying it. Some questions to ask:

  • How are they organizing their ideas?
  • What methods have they used to study the problem?
  • What theories have been used to explain, predict, or understand their research problem?
  • What sources have they cited to support their conclusions?
  • How have they used non-textual elements [e.g., charts, graphs, figures, etc.] to illustrate key points?

When you begin to write your literature review section, you'll be glad you dug deeper into how the research was designed and constructed because it establishes a means for developing more substantial analysis and interpretation of the research problem.

Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1 998.

Yet Another Writing Tip

When Do I Know I Can Stop Looking and Move On?

Here are several strategies you can utilize to assess whether you've thoroughly reviewed the literature:

  • Look for repeating patterns in the research findings . If the same thing is being said, just by different people, then this likely demonstrates that the research problem has hit a conceptual dead end. At this point consider: Does your study extend current research?  Does it forge a new path? Or, does is merely add more of the same thing being said?
  • Look at sources the authors cite to in their work . If you begin to see the same researchers cited again and again, then this is often an indication that no new ideas have been generated to address the research problem.
  • Search Google Scholar to identify who has subsequently cited leading scholars already identified in your literature review [see next sub-tab]. This is called citation tracking and there are a number of sources that can help you identify who has cited whom, particularly scholars from outside of your discipline. Here again, if the same authors are being cited again and again, this may indicate no new literature has been written on the topic.

Onwuegbuzie, Anthony J. and Rebecca Frels. Seven Steps to a Comprehensive Literature Review: A Multimodal and Cultural Approach . Los Angeles, CA: Sage, 2016; Sutton, Anthea. Systematic Approaches to a Successful Literature Review . Los Angeles, CA: Sage Publications, 2016.

  • << Previous: Theoretical Framework
  • Next: Citation Tracking >>
  • Last Updated: Mar 21, 2024 9:59 AM
  • URL: https://libguides.usc.edu/writingguide

Penn State University Libraries

Soc 001: introductory sociology.

  • Literature Reviews: Strategies for Writing
  • Fake News and Evaluating Sources

Literature Reviews

What is a Literature Review? The literature review is a critical look at the existing research that is significant to the work that you are carrying out. This overview identifies prominent research trends in addition to assessing the overall strengths and weaknesses of the existing research.

Purpose of the Literature Review

  • To provide background information about a research topic.
  • To establish the importance of a topic.
  • To demonstrate familiarity with a topic/problem.
  • To “carve out a space” for further work and allow you to position yourself in a scholarly conversation.

Characteristics of an effective literature review In addition to fulfilling the purposes outlined above, an effective literature review provides a critical overview of existing research by

  • Outlining important research trends.
  • Assessing strengths and weaknesses (of individual studies as well the existing research as a whole).
  • Identifying potential gaps in knowledge.
  • Establishing a need for current and/or future research projects.

Steps of the Literature Review Process

1) Planning: identify the focus, type, scope and discipline of the review you intend to write. 2) Reading and Research: collect and read current research on your topic. Select only those sources that are most relevant to your project. 3) Analyzing: summarize, synthesize, critique, and compare your sources in order to assess the field of research as a whole. 4) Drafting: develop a thesis or claim to make about the existing research and decide how to organize your material. 5) Revising: revise and finalize the structural, stylistic, and grammatical issues of your paper.

This process is not always a linear process; depending on the size and scope of your literature review, you may find yourself returning to some of these steps repeatedly as you continue to focus your project.

These steps adapted from the full workshop offered by the Graduate Writing Center at Penn State. 

Literature Review Format

 Introduction

  • Provide an overview of the topic, theme, or issue.
  • Identify your specific area of focus.
  • Describe your methodology and rationale. How did you decide which sources to include and which to exclude? Why? How is your review organized?
  • Briefly discuss the overall trends in the published scholarship in this area.
  •  Establish your reason for writing the review.
  •  Find the best organizational method for your review.
  •  Summarize sources by providing the most relevant information.
  •  Respectfully and objectively critique and evaluate the studies.
  •  Use direct quotations sparingly and only if appropriate.

 Conclusion

  •  Summarize the major findings of the sources that you reviewed, remembering to keep the focus on your topic.
  •  Evaluate the current state of scholarship in this area (ex. flaws or gaps in the research, inconsistencies in findings) 
  •  Identify any areas for further research.
  •  Conclude by making a connection between your topic and some larger area of study such as the discipline. 
  • << Previous: Home
  • Next: Fake News and Evaluating Sources >>
  • Last Updated: Oct 20, 2023 10:48 AM
  • URL: https://guides.libraries.psu.edu/shenangosoc001

U.S. flag

An official website of the United States government

The .gov means it's official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you're on a federal government site.

The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

  • Publications
  • Account settings
  • Browse Titles

NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health.

Lau F, Kuziemsky C, editors. Handbook of eHealth Evaluation: An Evidence-based Approach [Internet]. Victoria (BC): University of Victoria; 2017 Feb 27.

Cover of Handbook of eHealth Evaluation: An Evidence-based Approach

Handbook of eHealth Evaluation: An Evidence-based Approach [Internet].

Chapter 9 methods for literature reviews.

Guy Paré and Spyros Kitsiou .

9.1. Introduction

Literature reviews play a critical role in scholarship because science remains, first and foremost, a cumulative endeavour ( vom Brocke et al., 2009 ). As in any academic discipline, rigorous knowledge syntheses are becoming indispensable in keeping up with an exponentially growing eHealth literature, assisting practitioners, academics, and graduate students in finding, evaluating, and synthesizing the contents of many empirical and conceptual papers. Among other methods, literature reviews are essential for: (a) identifying what has been written on a subject or topic; (b) determining the extent to which a specific research area reveals any interpretable trends or patterns; (c) aggregating empirical findings related to a narrow research question to support evidence-based practice; (d) generating new frameworks and theories; and (e) identifying topics or questions requiring more investigation ( Paré, Trudel, Jaana, & Kitsiou, 2015 ).

Literature reviews can take two major forms. The most prevalent one is the “literature review” or “background” section within a journal paper or a chapter in a graduate thesis. This section synthesizes the extant literature and usually identifies the gaps in knowledge that the empirical study addresses ( Sylvester, Tate, & Johnstone, 2013 ). It may also provide a theoretical foundation for the proposed study, substantiate the presence of the research problem, justify the research as one that contributes something new to the cumulated knowledge, or validate the methods and approaches for the proposed study ( Hart, 1998 ; Levy & Ellis, 2006 ).

The second form of literature review, which is the focus of this chapter, constitutes an original and valuable work of research in and of itself ( Paré et al., 2015 ). Rather than providing a base for a researcher’s own work, it creates a solid starting point for all members of the community interested in a particular area or topic ( Mulrow, 1987 ). The so-called “review article” is a journal-length paper which has an overarching purpose to synthesize the literature in a field, without collecting or analyzing any primary data ( Green, Johnson, & Adams, 2006 ).

When appropriately conducted, review articles represent powerful information sources for practitioners looking for state-of-the art evidence to guide their decision-making and work practices ( Paré et al., 2015 ). Further, high-quality reviews become frequently cited pieces of work which researchers seek out as a first clear outline of the literature when undertaking empirical studies ( Cooper, 1988 ; Rowe, 2014 ). Scholars who track and gauge the impact of articles have found that review papers are cited and downloaded more often than any other type of published article ( Cronin, Ryan, & Coughlan, 2008 ; Montori, Wilczynski, Morgan, Haynes, & Hedges, 2003 ; Patsopoulos, Analatos, & Ioannidis, 2005 ). The reason for their popularity may be the fact that reading the review enables one to have an overview, if not a detailed knowledge of the area in question, as well as references to the most useful primary sources ( Cronin et al., 2008 ). Although they are not easy to conduct, the commitment to complete a review article provides a tremendous service to one’s academic community ( Paré et al., 2015 ; Petticrew & Roberts, 2006 ). Most, if not all, peer-reviewed journals in the fields of medical informatics publish review articles of some type.

The main objectives of this chapter are fourfold: (a) to provide an overview of the major steps and activities involved in conducting a stand-alone literature review; (b) to describe and contrast the different types of review articles that can contribute to the eHealth knowledge base; (c) to illustrate each review type with one or two examples from the eHealth literature; and (d) to provide a series of recommendations for prospective authors of review articles in this domain.

9.2. Overview of the Literature Review Process and Steps

As explained in Templier and Paré (2015) , there are six generic steps involved in conducting a review article:

  • formulating the research question(s) and objective(s),
  • searching the extant literature,
  • screening for inclusion,
  • assessing the quality of primary studies,
  • extracting data, and
  • analyzing data.

Although these steps are presented here in sequential order, one must keep in mind that the review process can be iterative and that many activities can be initiated during the planning stage and later refined during subsequent phases ( Finfgeld-Connett & Johnson, 2013 ; Kitchenham & Charters, 2007 ).

Formulating the research question(s) and objective(s): As a first step, members of the review team must appropriately justify the need for the review itself ( Petticrew & Roberts, 2006 ), identify the review’s main objective(s) ( Okoli & Schabram, 2010 ), and define the concepts or variables at the heart of their synthesis ( Cooper & Hedges, 2009 ; Webster & Watson, 2002 ). Importantly, they also need to articulate the research question(s) they propose to investigate ( Kitchenham & Charters, 2007 ). In this regard, we concur with Jesson, Matheson, and Lacey (2011) that clearly articulated research questions are key ingredients that guide the entire review methodology; they underscore the type of information that is needed, inform the search for and selection of relevant literature, and guide or orient the subsequent analysis. Searching the extant literature: The next step consists of searching the literature and making decisions about the suitability of material to be considered in the review ( Cooper, 1988 ). There exist three main coverage strategies. First, exhaustive coverage means an effort is made to be as comprehensive as possible in order to ensure that all relevant studies, published and unpublished, are included in the review and, thus, conclusions are based on this all-inclusive knowledge base. The second type of coverage consists of presenting materials that are representative of most other works in a given field or area. Often authors who adopt this strategy will search for relevant articles in a small number of top-tier journals in a field ( Paré et al., 2015 ). In the third strategy, the review team concentrates on prior works that have been central or pivotal to a particular topic. This may include empirical studies or conceptual papers that initiated a line of investigation, changed how problems or questions were framed, introduced new methods or concepts, or engendered important debate ( Cooper, 1988 ). Screening for inclusion: The following step consists of evaluating the applicability of the material identified in the preceding step ( Levy & Ellis, 2006 ; vom Brocke et al., 2009 ). Once a group of potential studies has been identified, members of the review team must screen them to determine their relevance ( Petticrew & Roberts, 2006 ). A set of predetermined rules provides a basis for including or excluding certain studies. This exercise requires a significant investment on the part of researchers, who must ensure enhanced objectivity and avoid biases or mistakes. As discussed later in this chapter, for certain types of reviews there must be at least two independent reviewers involved in the screening process and a procedure to resolve disagreements must also be in place ( Liberati et al., 2009 ; Shea et al., 2009 ). Assessing the quality of primary studies: In addition to screening material for inclusion, members of the review team may need to assess the scientific quality of the selected studies, that is, appraise the rigour of the research design and methods. Such formal assessment, which is usually conducted independently by at least two coders, helps members of the review team refine which studies to include in the final sample, determine whether or not the differences in quality may affect their conclusions, or guide how they analyze the data and interpret the findings ( Petticrew & Roberts, 2006 ). Ascribing quality scores to each primary study or considering through domain-based evaluations which study components have or have not been designed and executed appropriately makes it possible to reflect on the extent to which the selected study addresses possible biases and maximizes validity ( Shea et al., 2009 ). Extracting data: The following step involves gathering or extracting applicable information from each primary study included in the sample and deciding what is relevant to the problem of interest ( Cooper & Hedges, 2009 ). Indeed, the type of data that should be recorded mainly depends on the initial research questions ( Okoli & Schabram, 2010 ). However, important information may also be gathered about how, when, where and by whom the primary study was conducted, the research design and methods, or qualitative/quantitative results ( Cooper & Hedges, 2009 ). Analyzing and synthesizing data : As a final step, members of the review team must collate, summarize, aggregate, organize, and compare the evidence extracted from the included studies. The extracted data must be presented in a meaningful way that suggests a new contribution to the extant literature ( Jesson et al., 2011 ). Webster and Watson (2002) warn researchers that literature reviews should be much more than lists of papers and should provide a coherent lens to make sense of extant knowledge on a given topic. There exist several methods and techniques for synthesizing quantitative (e.g., frequency analysis, meta-analysis) and qualitative (e.g., grounded theory, narrative analysis, meta-ethnography) evidence ( Dixon-Woods, Agarwal, Jones, Young, & Sutton, 2005 ; Thomas & Harden, 2008 ).

9.3. Types of Review Articles and Brief Illustrations

EHealth researchers have at their disposal a number of approaches and methods for making sense out of existing literature, all with the purpose of casting current research findings into historical contexts or explaining contradictions that might exist among a set of primary research studies conducted on a particular topic. Our classification scheme is largely inspired from Paré and colleagues’ (2015) typology. Below we present and illustrate those review types that we feel are central to the growth and development of the eHealth domain.

9.3.1. Narrative Reviews

The narrative review is the “traditional” way of reviewing the extant literature and is skewed towards a qualitative interpretation of prior knowledge ( Sylvester et al., 2013 ). Put simply, a narrative review attempts to summarize or synthesize what has been written on a particular topic but does not seek generalization or cumulative knowledge from what is reviewed ( Davies, 2000 ; Green et al., 2006 ). Instead, the review team often undertakes the task of accumulating and synthesizing the literature to demonstrate the value of a particular point of view ( Baumeister & Leary, 1997 ). As such, reviewers may selectively ignore or limit the attention paid to certain studies in order to make a point. In this rather unsystematic approach, the selection of information from primary articles is subjective, lacks explicit criteria for inclusion and can lead to biased interpretations or inferences ( Green et al., 2006 ). There are several narrative reviews in the particular eHealth domain, as in all fields, which follow such an unstructured approach ( Silva et al., 2015 ; Paul et al., 2015 ).

Despite these criticisms, this type of review can be very useful in gathering together a volume of literature in a specific subject area and synthesizing it. As mentioned above, its primary purpose is to provide the reader with a comprehensive background for understanding current knowledge and highlighting the significance of new research ( Cronin et al., 2008 ). Faculty like to use narrative reviews in the classroom because they are often more up to date than textbooks, provide a single source for students to reference, and expose students to peer-reviewed literature ( Green et al., 2006 ). For researchers, narrative reviews can inspire research ideas by identifying gaps or inconsistencies in a body of knowledge, thus helping researchers to determine research questions or formulate hypotheses. Importantly, narrative reviews can also be used as educational articles to bring practitioners up to date with certain topics of issues ( Green et al., 2006 ).

Recently, there have been several efforts to introduce more rigour in narrative reviews that will elucidate common pitfalls and bring changes into their publication standards. Information systems researchers, among others, have contributed to advancing knowledge on how to structure a “traditional” review. For instance, Levy and Ellis (2006) proposed a generic framework for conducting such reviews. Their model follows the systematic data processing approach comprised of three steps, namely: (a) literature search and screening; (b) data extraction and analysis; and (c) writing the literature review. They provide detailed and very helpful instructions on how to conduct each step of the review process. As another methodological contribution, vom Brocke et al. (2009) offered a series of guidelines for conducting literature reviews, with a particular focus on how to search and extract the relevant body of knowledge. Last, Bandara, Miskon, and Fielt (2011) proposed a structured, predefined and tool-supported method to identify primary studies within a feasible scope, extract relevant content from identified articles, synthesize and analyze the findings, and effectively write and present the results of the literature review. We highly recommend that prospective authors of narrative reviews consult these useful sources before embarking on their work.

Darlow and Wen (2015) provide a good example of a highly structured narrative review in the eHealth field. These authors synthesized published articles that describe the development process of mobile health ( m-health ) interventions for patients’ cancer care self-management. As in most narrative reviews, the scope of the research questions being investigated is broad: (a) how development of these systems are carried out; (b) which methods are used to investigate these systems; and (c) what conclusions can be drawn as a result of the development of these systems. To provide clear answers to these questions, a literature search was conducted on six electronic databases and Google Scholar . The search was performed using several terms and free text words, combining them in an appropriate manner. Four inclusion and three exclusion criteria were utilized during the screening process. Both authors independently reviewed each of the identified articles to determine eligibility and extract study information. A flow diagram shows the number of studies identified, screened, and included or excluded at each stage of study selection. In terms of contributions, this review provides a series of practical recommendations for m-health intervention development.

9.3.2. Descriptive or Mapping Reviews

The primary goal of a descriptive review is to determine the extent to which a body of knowledge in a particular research topic reveals any interpretable pattern or trend with respect to pre-existing propositions, theories, methodologies or findings ( King & He, 2005 ; Paré et al., 2015 ). In contrast with narrative reviews, descriptive reviews follow a systematic and transparent procedure, including searching, screening and classifying studies ( Petersen, Vakkalanka, & Kuzniarz, 2015 ). Indeed, structured search methods are used to form a representative sample of a larger group of published works ( Paré et al., 2015 ). Further, authors of descriptive reviews extract from each study certain characteristics of interest, such as publication year, research methods, data collection techniques, and direction or strength of research outcomes (e.g., positive, negative, or non-significant) in the form of frequency analysis to produce quantitative results ( Sylvester et al., 2013 ). In essence, each study included in a descriptive review is treated as the unit of analysis and the published literature as a whole provides a database from which the authors attempt to identify any interpretable trends or draw overall conclusions about the merits of existing conceptualizations, propositions, methods or findings ( Paré et al., 2015 ). In doing so, a descriptive review may claim that its findings represent the state of the art in a particular domain ( King & He, 2005 ).

In the fields of health sciences and medical informatics, reviews that focus on examining the range, nature and evolution of a topic area are described by Anderson, Allen, Peckham, and Goodwin (2008) as mapping reviews . Like descriptive reviews, the research questions are generic and usually relate to publication patterns and trends. There is no preconceived plan to systematically review all of the literature although this can be done. Instead, researchers often present studies that are representative of most works published in a particular area and they consider a specific time frame to be mapped.

An example of this approach in the eHealth domain is offered by DeShazo, Lavallie, and Wolf (2009). The purpose of this descriptive or mapping review was to characterize publication trends in the medical informatics literature over a 20-year period (1987 to 2006). To achieve this ambitious objective, the authors performed a bibliometric analysis of medical informatics citations indexed in medline using publication trends, journal frequencies, impact factors, Medical Subject Headings (MeSH) term frequencies, and characteristics of citations. Findings revealed that there were over 77,000 medical informatics articles published during the covered period in numerous journals and that the average annual growth rate was 12%. The MeSH term analysis also suggested a strong interdisciplinary trend. Finally, average impact scores increased over time with two notable growth periods. Overall, patterns in research outputs that seem to characterize the historic trends and current components of the field of medical informatics suggest it may be a maturing discipline (DeShazo et al., 2009).

9.3.3. Scoping Reviews

Scoping reviews attempt to provide an initial indication of the potential size and nature of the extant literature on an emergent topic (Arksey & O’Malley, 2005; Daudt, van Mossel, & Scott, 2013 ; Levac, Colquhoun, & O’Brien, 2010). A scoping review may be conducted to examine the extent, range and nature of research activities in a particular area, determine the value of undertaking a full systematic review (discussed next), or identify research gaps in the extant literature ( Paré et al., 2015 ). In line with their main objective, scoping reviews usually conclude with the presentation of a detailed research agenda for future works along with potential implications for both practice and research.

Unlike narrative and descriptive reviews, the whole point of scoping the field is to be as comprehensive as possible, including grey literature (Arksey & O’Malley, 2005). Inclusion and exclusion criteria must be established to help researchers eliminate studies that are not aligned with the research questions. It is also recommended that at least two independent coders review abstracts yielded from the search strategy and then the full articles for study selection ( Daudt et al., 2013 ). The synthesized evidence from content or thematic analysis is relatively easy to present in tabular form (Arksey & O’Malley, 2005; Thomas & Harden, 2008 ).

One of the most highly cited scoping reviews in the eHealth domain was published by Archer, Fevrier-Thomas, Lokker, McKibbon, and Straus (2011) . These authors reviewed the existing literature on personal health record ( phr ) systems including design, functionality, implementation, applications, outcomes, and benefits. Seven databases were searched from 1985 to March 2010. Several search terms relating to phr s were used during this process. Two authors independently screened titles and abstracts to determine inclusion status. A second screen of full-text articles, again by two independent members of the research team, ensured that the studies described phr s. All in all, 130 articles met the criteria and their data were extracted manually into a database. The authors concluded that although there is a large amount of survey, observational, cohort/panel, and anecdotal evidence of phr benefits and satisfaction for patients, more research is needed to evaluate the results of phr implementations. Their in-depth analysis of the literature signalled that there is little solid evidence from randomized controlled trials or other studies through the use of phr s. Hence, they suggested that more research is needed that addresses the current lack of understanding of optimal functionality and usability of these systems, and how they can play a beneficial role in supporting patient self-management ( Archer et al., 2011 ).

9.3.4. Forms of Aggregative Reviews

Healthcare providers, practitioners, and policy-makers are nowadays overwhelmed with large volumes of information, including research-based evidence from numerous clinical trials and evaluation studies, assessing the effectiveness of health information technologies and interventions ( Ammenwerth & de Keizer, 2004 ; Deshazo et al., 2009 ). It is unrealistic to expect that all these disparate actors will have the time, skills, and necessary resources to identify the available evidence in the area of their expertise and consider it when making decisions. Systematic reviews that involve the rigorous application of scientific strategies aimed at limiting subjectivity and bias (i.e., systematic and random errors) can respond to this challenge.

Systematic reviews attempt to aggregate, appraise, and synthesize in a single source all empirical evidence that meet a set of previously specified eligibility criteria in order to answer a clearly formulated and often narrow research question on a particular topic of interest to support evidence-based practice ( Liberati et al., 2009 ). They adhere closely to explicit scientific principles ( Liberati et al., 2009 ) and rigorous methodological guidelines (Higgins & Green, 2008) aimed at reducing random and systematic errors that can lead to deviations from the truth in results or inferences. The use of explicit methods allows systematic reviews to aggregate a large body of research evidence, assess whether effects or relationships are in the same direction and of the same general magnitude, explain possible inconsistencies between study results, and determine the strength of the overall evidence for every outcome of interest based on the quality of included studies and the general consistency among them ( Cook, Mulrow, & Haynes, 1997 ). The main procedures of a systematic review involve:

  • Formulating a review question and developing a search strategy based on explicit inclusion criteria for the identification of eligible studies (usually described in the context of a detailed review protocol).
  • Searching for eligible studies using multiple databases and information sources, including grey literature sources, without any language restrictions.
  • Selecting studies, extracting data, and assessing risk of bias in a duplicate manner using two independent reviewers to avoid random or systematic errors in the process.
  • Analyzing data using quantitative or qualitative methods.
  • Presenting results in summary of findings tables.
  • Interpreting results and drawing conclusions.

Many systematic reviews, but not all, use statistical methods to combine the results of independent studies into a single quantitative estimate or summary effect size. Known as meta-analyses , these reviews use specific data extraction and statistical techniques (e.g., network, frequentist, or Bayesian meta-analyses) to calculate from each study by outcome of interest an effect size along with a confidence interval that reflects the degree of uncertainty behind the point estimate of effect ( Borenstein, Hedges, Higgins, & Rothstein, 2009 ; Deeks, Higgins, & Altman, 2008 ). Subsequently, they use fixed or random-effects analysis models to combine the results of the included studies, assess statistical heterogeneity, and calculate a weighted average of the effect estimates from the different studies, taking into account their sample sizes. The summary effect size is a value that reflects the average magnitude of the intervention effect for a particular outcome of interest or, more generally, the strength of a relationship between two variables across all studies included in the systematic review. By statistically combining data from multiple studies, meta-analyses can create more precise and reliable estimates of intervention effects than those derived from individual studies alone, when these are examined independently as discrete sources of information.

The review by Gurol-Urganci, de Jongh, Vodopivec-Jamsek, Atun, and Car (2013) on the effects of mobile phone messaging reminders for attendance at healthcare appointments is an illustrative example of a high-quality systematic review with meta-analysis. Missed appointments are a major cause of inefficiency in healthcare delivery with substantial monetary costs to health systems. These authors sought to assess whether mobile phone-based appointment reminders delivered through Short Message Service ( sms ) or Multimedia Messaging Service ( mms ) are effective in improving rates of patient attendance and reducing overall costs. To this end, they conducted a comprehensive search on multiple databases using highly sensitive search strategies without language or publication-type restrictions to identify all rct s that are eligible for inclusion. In order to minimize the risk of omitting eligible studies not captured by the original search, they supplemented all electronic searches with manual screening of trial registers and references contained in the included studies. Study selection, data extraction, and risk of bias assessments were performed inde­­pen­dently by two coders using standardized methods to ensure consistency and to eliminate potential errors. Findings from eight rct s involving 6,615 participants were pooled into meta-analyses to calculate the magnitude of effects that mobile text message reminders have on the rate of attendance at healthcare appointments compared to no reminders and phone call reminders.

Meta-analyses are regarded as powerful tools for deriving meaningful conclusions. However, there are situations in which it is neither reasonable nor appropriate to pool studies together using meta-analytic methods simply because there is extensive clinical heterogeneity between the included studies or variation in measurement tools, comparisons, or outcomes of interest. In these cases, systematic reviews can use qualitative synthesis methods such as vote counting, content analysis, classification schemes and tabulations, as an alternative approach to narratively synthesize the results of the independent studies included in the review. This form of review is known as qualitative systematic review.

A rigorous example of one such review in the eHealth domain is presented by Mickan, Atherton, Roberts, Heneghan, and Tilson (2014) on the use of handheld computers by healthcare professionals and their impact on access to information and clinical decision-making. In line with the methodological guide­lines for systematic reviews, these authors: (a) developed and registered with prospero ( www.crd.york.ac.uk/ prospero / ) an a priori review protocol; (b) conducted comprehensive searches for eligible studies using multiple databases and other supplementary strategies (e.g., forward searches); and (c) subsequently carried out study selection, data extraction, and risk of bias assessments in a duplicate manner to eliminate potential errors in the review process. Heterogeneity between the included studies in terms of reported outcomes and measures precluded the use of meta-analytic methods. To this end, the authors resorted to using narrative analysis and synthesis to describe the effectiveness of handheld computers on accessing information for clinical knowledge, adherence to safety and clinical quality guidelines, and diagnostic decision-making.

In recent years, the number of systematic reviews in the field of health informatics has increased considerably. Systematic reviews with discordant findings can cause great confusion and make it difficult for decision-makers to interpret the review-level evidence ( Moher, 2013 ). Therefore, there is a growing need for appraisal and synthesis of prior systematic reviews to ensure that decision-making is constantly informed by the best available accumulated evidence. Umbrella reviews , also known as overviews of systematic reviews, are tertiary types of evidence synthesis that aim to accomplish this; that is, they aim to compare and contrast findings from multiple systematic reviews and meta-analyses ( Becker & Oxman, 2008 ). Umbrella reviews generally adhere to the same principles and rigorous methodological guidelines used in systematic reviews. However, the unit of analysis in umbrella reviews is the systematic review rather than the primary study ( Becker & Oxman, 2008 ). Unlike systematic reviews that have a narrow focus of inquiry, umbrella reviews focus on broader research topics for which there are several potential interventions ( Smith, Devane, Begley, & Clarke, 2011 ). A recent umbrella review on the effects of home telemonitoring interventions for patients with heart failure critically appraised, compared, and synthesized evidence from 15 systematic reviews to investigate which types of home telemonitoring technologies and forms of interventions are more effective in reducing mortality and hospital admissions ( Kitsiou, Paré, & Jaana, 2015 ).

9.3.5. Realist Reviews

Realist reviews are theory-driven interpretative reviews developed to inform, enhance, or supplement conventional systematic reviews by making sense of heterogeneous evidence about complex interventions applied in diverse contexts in a way that informs policy decision-making ( Greenhalgh, Wong, Westhorp, & Pawson, 2011 ). They originated from criticisms of positivist systematic reviews which centre on their “simplistic” underlying assumptions ( Oates, 2011 ). As explained above, systematic reviews seek to identify causation. Such logic is appropriate for fields like medicine and education where findings of randomized controlled trials can be aggregated to see whether a new treatment or intervention does improve outcomes. However, many argue that it is not possible to establish such direct causal links between interventions and outcomes in fields such as social policy, management, and information systems where for any intervention there is unlikely to be a regular or consistent outcome ( Oates, 2011 ; Pawson, 2006 ; Rousseau, Manning, & Denyer, 2008 ).

To circumvent these limitations, Pawson, Greenhalgh, Harvey, and Walshe (2005) have proposed a new approach for synthesizing knowledge that seeks to unpack the mechanism of how “complex interventions” work in particular contexts. The basic research question — what works? — which is usually associated with systematic reviews changes to: what is it about this intervention that works, for whom, in what circumstances, in what respects and why? Realist reviews have no particular preference for either quantitative or qualitative evidence. As a theory-building approach, a realist review usually starts by articulating likely underlying mechanisms and then scrutinizes available evidence to find out whether and where these mechanisms are applicable ( Shepperd et al., 2009 ). Primary studies found in the extant literature are viewed as case studies which can test and modify the initial theories ( Rousseau et al., 2008 ).

The main objective pursued in the realist review conducted by Otte-Trojel, de Bont, Rundall, and van de Klundert (2014) was to examine how patient portals contribute to health service delivery and patient outcomes. The specific goals were to investigate how outcomes are produced and, most importantly, how variations in outcomes can be explained. The research team started with an exploratory review of background documents and research studies to identify ways in which patient portals may contribute to health service delivery and patient outcomes. The authors identified six main ways which represent “educated guesses” to be tested against the data in the evaluation studies. These studies were identified through a formal and systematic search in four databases between 2003 and 2013. Two members of the research team selected the articles using a pre-established list of inclusion and exclusion criteria and following a two-step procedure. The authors then extracted data from the selected articles and created several tables, one for each outcome category. They organized information to bring forward those mechanisms where patient portals contribute to outcomes and the variation in outcomes across different contexts.

9.3.6. Critical Reviews

Lastly, critical reviews aim to provide a critical evaluation and interpretive analysis of existing literature on a particular topic of interest to reveal strengths, weaknesses, contradictions, controversies, inconsistencies, and/or other important issues with respect to theories, hypotheses, research methods or results ( Baumeister & Leary, 1997 ; Kirkevold, 1997 ). Unlike other review types, critical reviews attempt to take a reflective account of the research that has been done in a particular area of interest, and assess its credibility by using appraisal instruments or critical interpretive methods. In this way, critical reviews attempt to constructively inform other scholars about the weaknesses of prior research and strengthen knowledge development by giving focus and direction to studies for further improvement ( Kirkevold, 1997 ).

Kitsiou, Paré, and Jaana (2013) provide an example of a critical review that assessed the methodological quality of prior systematic reviews of home telemonitoring studies for chronic patients. The authors conducted a comprehensive search on multiple databases to identify eligible reviews and subsequently used a validated instrument to conduct an in-depth quality appraisal. Results indicate that the majority of systematic reviews in this particular area suffer from important methodological flaws and biases that impair their internal validity and limit their usefulness for clinical and decision-making purposes. To this end, they provide a number of recommendations to strengthen knowledge development towards improving the design and execution of future reviews on home telemonitoring.

9.4. Summary

Table 9.1 outlines the main types of literature reviews that were described in the previous sub-sections and summarizes the main characteristics that distinguish one review type from another. It also includes key references to methodological guidelines and useful sources that can be used by eHealth scholars and researchers for planning and developing reviews.

Table 9.1. Typology of Literature Reviews (adapted from Paré et al., 2015).

Typology of Literature Reviews (adapted from Paré et al., 2015).

As shown in Table 9.1 , each review type addresses different kinds of research questions or objectives, which subsequently define and dictate the methods and approaches that need to be used to achieve the overarching goal(s) of the review. For example, in the case of narrative reviews, there is greater flexibility in searching and synthesizing articles ( Green et al., 2006 ). Researchers are often relatively free to use a diversity of approaches to search, identify, and select relevant scientific articles, describe their operational characteristics, present how the individual studies fit together, and formulate conclusions. On the other hand, systematic reviews are characterized by their high level of systematicity, rigour, and use of explicit methods, based on an “a priori” review plan that aims to minimize bias in the analysis and synthesis process (Higgins & Green, 2008). Some reviews are exploratory in nature (e.g., scoping/mapping reviews), whereas others may be conducted to discover patterns (e.g., descriptive reviews) or involve a synthesis approach that may include the critical analysis of prior research ( Paré et al., 2015 ). Hence, in order to select the most appropriate type of review, it is critical to know before embarking on a review project, why the research synthesis is conducted and what type of methods are best aligned with the pursued goals.

9.5. Concluding Remarks

In light of the increased use of evidence-based practice and research generating stronger evidence ( Grady et al., 2011 ; Lyden et al., 2013 ), review articles have become essential tools for summarizing, synthesizing, integrating or critically appraising prior knowledge in the eHealth field. As mentioned earlier, when rigorously conducted review articles represent powerful information sources for eHealth scholars and practitioners looking for state-of-the-art evidence. The typology of literature reviews we used herein will allow eHealth researchers, graduate students and practitioners to gain a better understanding of the similarities and differences between review types.

We must stress that this classification scheme does not privilege any specific type of review as being of higher quality than another ( Paré et al., 2015 ). As explained above, each type of review has its own strengths and limitations. Having said that, we realize that the methodological rigour of any review — be it qualitative, quantitative or mixed — is a critical aspect that should be considered seriously by prospective authors. In the present context, the notion of rigour refers to the reliability and validity of the review process described in section 9.2. For one thing, reliability is related to the reproducibility of the review process and steps, which is facilitated by a comprehensive documentation of the literature search process, extraction, coding and analysis performed in the review. Whether the search is comprehensive or not, whether it involves a methodical approach for data extraction and synthesis or not, it is important that the review documents in an explicit and transparent manner the steps and approach that were used in the process of its development. Next, validity characterizes the degree to which the review process was conducted appropriately. It goes beyond documentation and reflects decisions related to the selection of the sources, the search terms used, the period of time covered, the articles selected in the search, and the application of backward and forward searches ( vom Brocke et al., 2009 ). In short, the rigour of any review article is reflected by the explicitness of its methods (i.e., transparency) and the soundness of the approach used. We refer those interested in the concepts of rigour and quality to the work of Templier and Paré (2015) which offers a detailed set of methodological guidelines for conducting and evaluating various types of review articles.

To conclude, our main objective in this chapter was to demystify the various types of literature reviews that are central to the continuous development of the eHealth field. It is our hope that our descriptive account will serve as a valuable source for those conducting, evaluating or using reviews in this important and growing domain.

  • Ammenwerth E., de Keizer N. An inventory of evaluation studies of information technology in health care. Trends in evaluation research, 1982-2002. International Journal of Medical Informatics. 2004; 44 (1):44–56. [ PubMed : 15778794 ]
  • Anderson S., Allen P., Peckham S., Goodwin N. Asking the right questions: scoping studies in the commissioning of research on the organisation and delivery of health services. Health Research Policy and Systems. 2008; 6 (7):1–12. [ PMC free article : PMC2500008 ] [ PubMed : 18613961 ] [ CrossRef ]
  • Archer N., Fevrier-Thomas U., Lokker C., McKibbon K. A., Straus S.E. Personal health records: a scoping review. Journal of American Medical Informatics Association. 2011; 18 (4):515–522. [ PMC free article : PMC3128401 ] [ PubMed : 21672914 ]
  • Arksey H., O’Malley L. Scoping studies: towards a methodological framework. International Journal of Social Research Methodology. 2005; 8 (1):19–32.
  • A systematic, tool-supported method for conducting literature reviews in information systems. Paper presented at the Proceedings of the 19th European Conference on Information Systems ( ecis 2011); June 9 to 11; Helsinki, Finland. 2011.
  • Baumeister R. F., Leary M.R. Writing narrative literature reviews. Review of General Psychology. 1997; 1 (3):311–320.
  • Becker L. A., Oxman A.D. In: Cochrane handbook for systematic reviews of interventions. Higgins J. P. T., Green S., editors. Hoboken, nj : John Wiley & Sons, Ltd; 2008. Overviews of reviews; pp. 607–631.
  • Borenstein M., Hedges L., Higgins J., Rothstein H. Introduction to meta-analysis. Hoboken, nj : John Wiley & Sons Inc; 2009.
  • Cook D. J., Mulrow C. D., Haynes B. Systematic reviews: Synthesis of best evidence for clinical decisions. Annals of Internal Medicine. 1997; 126 (5):376–380. [ PubMed : 9054282 ]
  • Cooper H., Hedges L.V. In: The handbook of research synthesis and meta-analysis. 2nd ed. Cooper H., Hedges L. V., Valentine J. C., editors. New York: Russell Sage Foundation; 2009. Research synthesis as a scientific process; pp. 3–17.
  • Cooper H. M. Organizing knowledge syntheses: A taxonomy of literature reviews. Knowledge in Society. 1988; 1 (1):104–126.
  • Cronin P., Ryan F., Coughlan M. Undertaking a literature review: a step-by-step approach. British Journal of Nursing. 2008; 17 (1):38–43. [ PubMed : 18399395 ]
  • Darlow S., Wen K.Y. Development testing of mobile health interventions for cancer patient self-management: A review. Health Informatics Journal. 2015 (online before print). [ PubMed : 25916831 ] [ CrossRef ]
  • Daudt H. M., van Mossel C., Scott S.J. Enhancing the scoping study methodology: a large, inter-professional team’s experience with Arksey and O’Malley’s framework. bmc Medical Research Methodology. 2013; 13 :48. [ PMC free article : PMC3614526 ] [ PubMed : 23522333 ] [ CrossRef ]
  • Davies P. The relevance of systematic reviews to educational policy and practice. Oxford Review of Education. 2000; 26 (3-4):365–378.
  • Deeks J. J., Higgins J. P. T., Altman D.G. In: Cochrane handbook for systematic reviews of interventions. Higgins J. P. T., Green S., editors. Hoboken, nj : John Wiley & Sons, Ltd; 2008. Analysing data and undertaking meta-analyses; pp. 243–296.
  • Deshazo J. P., Lavallie D. L., Wolf F.M. Publication trends in the medical informatics literature: 20 years of “Medical Informatics” in mesh . bmc Medical Informatics and Decision Making. 2009; 9 :7. [ PMC free article : PMC2652453 ] [ PubMed : 19159472 ] [ CrossRef ]
  • Dixon-Woods M., Agarwal S., Jones D., Young B., Sutton A. Synthesising qualitative and quantitative evidence: a review of possible methods. Journal of Health Services Research and Policy. 2005; 10 (1):45–53. [ PubMed : 15667704 ]
  • Finfgeld-Connett D., Johnson E.D. Literature search strategies for conducting knowledge-building and theory-generating qualitative systematic reviews. Journal of Advanced Nursing. 2013; 69 (1):194–204. [ PMC free article : PMC3424349 ] [ PubMed : 22591030 ]
  • Grady B., Myers K. M., Nelson E. L., Belz N., Bennett L., Carnahan L. … Guidelines Working Group. Evidence-based practice for telemental health. Telemedicine Journal and E Health. 2011; 17 (2):131–148. [ PubMed : 21385026 ]
  • Green B. N., Johnson C. D., Adams A. Writing narrative literature reviews for peer-reviewed journals: secrets of the trade. Journal of Chiropractic Medicine. 2006; 5 (3):101–117. [ PMC free article : PMC2647067 ] [ PubMed : 19674681 ]
  • Greenhalgh T., Wong G., Westhorp G., Pawson R. Protocol–realist and meta-narrative evidence synthesis: evolving standards ( rameses ). bmc Medical Research Methodology. 2011; 11 :115. [ PMC free article : PMC3173389 ] [ PubMed : 21843376 ]
  • Gurol-Urganci I., de Jongh T., Vodopivec-Jamsek V., Atun R., Car J. Mobile phone messaging reminders for attendance at healthcare appointments. Cochrane Database System Review. 2013; 12 cd 007458. [ PMC free article : PMC6485985 ] [ PubMed : 24310741 ] [ CrossRef ]
  • Hart C. Doing a literature review: Releasing the social science research imagination. London: SAGE Publications; 1998.
  • Higgins J. P. T., Green S., editors. Cochrane handbook for systematic reviews of interventions: Cochrane book series. Hoboken, nj : Wiley-Blackwell; 2008.
  • Jesson J., Matheson L., Lacey F.M. Doing your literature review: traditional and systematic techniques. Los Angeles & London: SAGE Publications; 2011.
  • King W. R., He J. Understanding the role and methods of meta-analysis in IS research. Communications of the Association for Information Systems. 2005; 16 :1.
  • Kirkevold M. Integrative nursing research — an important strategy to further the development of nursing science and nursing practice. Journal of Advanced Nursing. 1997; 25 (5):977–984. [ PubMed : 9147203 ]
  • Kitchenham B., Charters S. ebse Technical Report Version 2.3. Keele & Durham. uk : Keele University & University of Durham; 2007. Guidelines for performing systematic literature reviews in software engineering.
  • Kitsiou S., Paré G., Jaana M. Systematic reviews and meta-analyses of home telemonitoring interventions for patients with chronic diseases: a critical assessment of their methodological quality. Journal of Medical Internet Research. 2013; 15 (7):e150. [ PMC free article : PMC3785977 ] [ PubMed : 23880072 ]
  • Kitsiou S., Paré G., Jaana M. Effects of home telemonitoring interventions on patients with chronic heart failure: an overview of systematic reviews. Journal of Medical Internet Research. 2015; 17 (3):e63. [ PMC free article : PMC4376138 ] [ PubMed : 25768664 ]
  • Levac D., Colquhoun H., O’Brien K. K. Scoping studies: advancing the methodology. Implementation Science. 2010; 5 (1):69. [ PMC free article : PMC2954944 ] [ PubMed : 20854677 ]
  • Levy Y., Ellis T.J. A systems approach to conduct an effective literature review in support of information systems research. Informing Science. 2006; 9 :181–211.
  • Liberati A., Altman D. G., Tetzlaff J., Mulrow C., Gøtzsche P. C., Ioannidis J. P. A. et al. Moher D. The prisma statement for reporting systematic reviews and meta-analyses of studies that evaluate health care interventions: Explanation and elaboration. Annals of Internal Medicine. 2009; 151 (4):W-65. [ PubMed : 19622512 ]
  • Lyden J. R., Zickmund S. L., Bhargava T. D., Bryce C. L., Conroy M. B., Fischer G. S. et al. McTigue K. M. Implementing health information technology in a patient-centered manner: Patient experiences with an online evidence-based lifestyle intervention. Journal for Healthcare Quality. 2013; 35 (5):47–57. [ PubMed : 24004039 ]
  • Mickan S., Atherton H., Roberts N. W., Heneghan C., Tilson J.K. Use of handheld computers in clinical practice: a systematic review. bmc Medical Informatics and Decision Making. 2014; 14 :56. [ PMC free article : PMC4099138 ] [ PubMed : 24998515 ]
  • Moher D. The problem of duplicate systematic reviews. British Medical Journal. 2013; 347 (5040) [ PubMed : 23945367 ] [ CrossRef ]
  • Montori V. M., Wilczynski N. L., Morgan D., Haynes R. B., Hedges T. Systematic reviews: a cross-sectional study of location and citation counts. bmc Medicine. 2003; 1 :2. [ PMC free article : PMC281591 ] [ PubMed : 14633274 ]
  • Mulrow C. D. The medical review article: state of the science. Annals of Internal Medicine. 1987; 106 (3):485–488. [ PubMed : 3813259 ] [ CrossRef ]
  • Evidence-based information systems: A decade later. Proceedings of the European Conference on Information Systems ; 2011. Retrieved from http://aisel ​.aisnet.org/cgi/viewcontent ​.cgi?article ​=1221&context ​=ecis2011 .
  • Okoli C., Schabram K. A guide to conducting a systematic literature review of information systems research. ssrn Electronic Journal. 2010
  • Otte-Trojel T., de Bont A., Rundall T. G., van de Klundert J. How outcomes are achieved through patient portals: a realist review. Journal of American Medical Informatics Association. 2014; 21 (4):751–757. [ PMC free article : PMC4078283 ] [ PubMed : 24503882 ]
  • Paré G., Trudel M.-C., Jaana M., Kitsiou S. Synthesizing information systems knowledge: A typology of literature reviews. Information & Management. 2015; 52 (2):183–199.
  • Patsopoulos N. A., Analatos A. A., Ioannidis J.P. A. Relative citation impact of various study designs in the health sciences. Journal of the American Medical Association. 2005; 293 (19):2362–2366. [ PubMed : 15900006 ]
  • Paul M. M., Greene C. M., Newton-Dame R., Thorpe L. E., Perlman S. E., McVeigh K. H., Gourevitch M.N. The state of population health surveillance using electronic health records: A narrative review. Population Health Management. 2015; 18 (3):209–216. [ PubMed : 25608033 ]
  • Pawson R. Evidence-based policy: a realist perspective. London: SAGE Publications; 2006.
  • Pawson R., Greenhalgh T., Harvey G., Walshe K. Realist review—a new method of systematic review designed for complex policy interventions. Journal of Health Services Research & Policy. 2005; 10 (Suppl 1):21–34. [ PubMed : 16053581 ]
  • Petersen K., Vakkalanka S., Kuzniarz L. Guidelines for conducting systematic mapping studies in software engineering: An update. Information and Software Technology. 2015; 64 :1–18.
  • Petticrew M., Roberts H. Systematic reviews in the social sciences: A practical guide. Malden, ma : Blackwell Publishing Co; 2006.
  • Rousseau D. M., Manning J., Denyer D. Evidence in management and organizational science: Assembling the field’s full weight of scientific knowledge through syntheses. The Academy of Management Annals. 2008; 2 (1):475–515.
  • Rowe F. What literature review is not: diversity, boundaries and recommendations. European Journal of Information Systems. 2014; 23 (3):241–255.
  • Shea B. J., Hamel C., Wells G. A., Bouter L. M., Kristjansson E., Grimshaw J. et al. Boers M. amstar is a reliable and valid measurement tool to assess the methodological quality of systematic reviews. Journal of Clinical Epidemiology. 2009; 62 (10):1013–1020. [ PubMed : 19230606 ]
  • Shepperd S., Lewin S., Straus S., Clarke M., Eccles M. P., Fitzpatrick R. et al. Sheikh A. Can we systematically review studies that evaluate complex interventions? PLoS Medicine. 2009; 6 (8):e1000086. [ PMC free article : PMC2717209 ] [ PubMed : 19668360 ]
  • Silva B. M., Rodrigues J. J., de la Torre Díez I., López-Coronado M., Saleem K. Mobile-health: A review of current state in 2015. Journal of Biomedical Informatics. 2015; 56 :265–272. [ PubMed : 26071682 ]
  • Smith V., Devane D., Begley C., Clarke M. Methodology in conducting a systematic review of systematic reviews of healthcare interventions. bmc Medical Research Methodology. 2011; 11 (1):15. [ PMC free article : PMC3039637 ] [ PubMed : 21291558 ]
  • Sylvester A., Tate M., Johnstone D. Beyond synthesis: re-presenting heterogeneous research literature. Behaviour & Information Technology. 2013; 32 (12):1199–1215.
  • Templier M., Paré G. A framework for guiding and evaluating literature reviews. Communications of the Association for Information Systems. 2015; 37 (6):112–137.
  • Thomas J., Harden A. Methods for the thematic synthesis of qualitative research in systematic reviews. bmc Medical Research Methodology. 2008; 8 (1):45. [ PMC free article : PMC2478656 ] [ PubMed : 18616818 ]
  • Reconstructing the giant: on the importance of rigour in documenting the literature search process. Paper presented at the Proceedings of the 17th European Conference on Information Systems ( ecis 2009); Verona, Italy. 2009.
  • Webster J., Watson R.T. Analyzing the past to prepare for the future: Writing a literature review. Management Information Systems Quarterly. 2002; 26 (2):11.
  • Whitlock E. P., Lin J. S., Chou R., Shekelle P., Robinson K.A. Using existing systematic reviews in complex systematic reviews. Annals of Internal Medicine. 2008; 148 (10):776–782. [ PubMed : 18490690 ]

This publication is licensed under a Creative Commons License, Attribution-Noncommercial 4.0 International License (CC BY-NC 4.0): see https://creativecommons.org/licenses/by-nc/4.0/

  • Cite this Page Paré G, Kitsiou S. Chapter 9 Methods for Literature Reviews. In: Lau F, Kuziemsky C, editors. Handbook of eHealth Evaluation: An Evidence-based Approach [Internet]. Victoria (BC): University of Victoria; 2017 Feb 27.
  • PDF version of this title (4.5M)
  • Disable Glossary Links

In this Page

  • Introduction
  • Overview of the Literature Review Process and Steps
  • Types of Review Articles and Brief Illustrations
  • Concluding Remarks

Related information

  • PMC PubMed Central citations
  • PubMed Links to PubMed

Recent Activity

  • Chapter 9 Methods for Literature Reviews - Handbook of eHealth Evaluation: An Ev... Chapter 9 Methods for Literature Reviews - Handbook of eHealth Evaluation: An Evidence-based Approach

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

Connect with NLM

National Library of Medicine 8600 Rockville Pike Bethesda, MD 20894

Web Policies FOIA HHS Vulnerability Disclosure

Help Accessibility Careers

statistics

  • Locations and Hours
  • UCLA Library
  • Research Guides
  • Biomedical Library Guides

Systematic Reviews

  • Types of Literature Reviews

What Makes a Systematic Review Different from Other Types of Reviews?

  • Planning Your Systematic Review
  • Database Searching
  • Creating the Search
  • Search Filters & Hedges
  • Grey Literature
  • Managing & Appraising Results
  • Further Resources

Reproduced from Grant, M. J. and Booth, A. (2009), A typology of reviews: an analysis of 14 review types and associated methodologies. Health Information & Libraries Journal, 26: 91–108. doi:10.1111/j.1471-1842.2009.00848.x

  • << Previous: Home
  • Next: Planning Your Systematic Review >>
  • Last Updated: Mar 1, 2024 10:55 AM
  • URL: https://guides.library.ucla.edu/systematicreviews

The University of Edinburgh

  • Schools & departments

what are the characteristics of a literature review

Literature review

A general guide on how to conduct and write a literature review.

Please check course or programme information and materials provided by teaching staff, including your project supervisor, for subject-specific guidance.

What is a literature review?

A literature review is a piece of academic writing demonstrating knowledge and understanding of the academic literature on a specific topic placed in context.  A literature review also includes a critical evaluation of the material; this is why it is called a literature review rather than a literature report. It is a process of reviewing the literature, as well as a form of writing.

To illustrate the difference between reporting and reviewing, think about television or film review articles.  These articles include content such as a brief synopsis or the key points of the film or programme plus the critic’s own evaluation.  Similarly the two main objectives of a literature review are firstly the content covering existing research, theories and evidence, and secondly your own critical evaluation and discussion of this content. 

Usually a literature review forms a section or part of a dissertation, research project or long essay.  However, it can also be set and assessed as a standalone piece of work.

What is the purpose of a literature review?

…your task is to build an argument, not a library. Rudestam, K.E. and Newton, R.R. (1992) Surviving your dissertation: A comprehensive guide to content and process. California: Sage, p49.

In a larger piece of written work, such as a dissertation or project, a literature review is usually one of the first tasks carried out after deciding on a topic.  Reading combined with critical analysis can help to refine a topic and frame research questions.  Conducting a literature review establishes your familiarity with and understanding of current research in a particular field before carrying out a new investigation. After doing a literature review, you should know what research has already been done and be able to identify what is unknown within your topic.

When doing and writing a literature review, it is good practice to:

  • summarise and analyse previous research and theories;
  • identify areas of controversy and contested claims;
  • highlight any gaps that may exist in research to date.

Conducting a literature review

Focusing on different aspects of your literature review can be useful to help plan, develop, refine and write it.  You can use and adapt the prompt questions in our worksheet below at different points in the process of researching and writing your review.  These are suggestions to get you thinking and writing.

Developing and refining your literature review (pdf)

Developing and refining your literature review (Word)

Developing and refining your literature review (Word rtf)

Writing a literature review has a lot in common with other assignment tasks.  There is advice on our other pages about thinking critically, reading strategies and academic writing.  Our literature review top tips suggest some specific things you can do to help you submit a successful review.

Literature review top tips (pdf)

Literature review top tips (Word rtf)

Our reading page includes strategies and advice on using books and articles and a notes record sheet grid you can use.

Reading at university

The Academic writing page suggests ways to organise and structure information from a range of sources and how you can develop your argument as you read and write.

Academic writing

The Critical thinking page has advice on how to be a more critical researcher and a form you can use to help you think and break down the stages of developing your argument.

Critical thinking

As with other forms of academic writing, your literature review needs to demonstrate good academic practice by following the Code of Student Conduct and acknowledging the work of others through citing and referencing your sources.  

Good academic practice

As with any writing task, you will need to review, edit and rewrite sections of your literature review.  The Editing and proofreading page includes tips on how to do this and strategies for standing back and thinking about your structure and checking the flow of your argument.

Editing and proofreading

Guidance on literature searching from the University Library

The Academic Support Librarians have developed LibSmart I and II, Learn courses to help you develop and enhance your digital research skills and capabilities; from getting started with the Library to managing data for your dissertation.

Searching using the library’s DiscoverEd tool: DiscoverEd

Finding resources in your subject: Subject guides

The Academic Support Librarians also provide one-to-one appointments to help you develop your research strategies.

1 to 1 support for literature searching and systematic reviews

Advice to help you optimise use of Google Scholar, Google Books and Google for your research and study: Using Google

Managing and curating your references

A referencing management tool can help you to collect and organise and your source material to produce a bibliography or reference list. 

Referencing and reference management

Information Services provide access to Cite them right online which is a guide to the main referencing systems and tells you how to reference just about any source (EASE log-in may be required).

Cite them right

Published study guides

There are a number of scholarship skills books and guides available which can help with writing a literature review.  Our Resource List of study skills guides includes sections on Referencing, Dissertation and project writing and Literature reviews.

Study skills guides

Duke University Libraries

Literature Reviews

  • Types of reviews
  • Getting started

Types of reviews and examples

Choosing a review type.

  • 1. Define your research question
  • 2. Plan your search
  • 3. Search the literature
  • 4. Organize your results
  • 5. Synthesize your findings
  • 6. Write the review
  • Artificial intelligence (AI) tools
  • Thompson Writing Studio This link opens in a new window
  • Need to write a systematic review? This link opens in a new window

what are the characteristics of a literature review

Contact a Librarian

Ask a Librarian

Overview of types of literature reviews

Made with  Visme Infographic Maker

  • Meta-analysis
  • Systematized

Definition:

"A term used to describe a conventional overview of the literature, particularly when contrasted with a systematic review (Booth et al., 2012, p. 265).

Characteristics:

  • Provides examination of recent or current literature on a wide range of subjects
  • Varying levels of completeness / comprehensiveness, non-standardized methodology
  • May or may not include comprehensive searching, quality assessment or critical appraisal

Mitchell, L. E., & Zajchowski, C. A. (2022). The history of air quality in Utah: A narrative review.  Sustainability ,  14 (15), 9653.  doi.org/10.3390/su14159653

Booth, A., Papaioannou, D., & Sutton, A. (2012). Systematic approaches to a successful literature review. London: SAGE Publications Ltd.

"An assessment of what is already known about a policy or practice issue...using systematic review methods to search and critically appraise existing research" (Grant & Booth, 2009, p. 100).

  • Assessment of what is already known about an issue
  • Similar to a systematic review but within a time-constrained setting
  • Typically employs methodological shortcuts, increasing risk of introducing bias, includes basic level of quality assessment
  • Best suited for issues needing quick decisions and solutions (i.e., policy recommendations)

Learn more about the method:

Khangura, S., Konnyu, K., Cushman, R., Grimshaw, J., & Moher, D. (2012). Evidence summaries: the evolution of a rapid review approach.  Systematic reviews, 1 (1), 1-9.  https://doi.org/10.1186/2046-4053-1-10

Virginia Commonwealth University Libraries. (2021). Rapid Review Protocol .

Quarmby, S., Santos, G., & Mathias, M. (2019). Air quality strategies and technologies: A rapid review of the international evidence.  Sustainability, 11 (10), 2757.  https://doi.org/10.3390/su11102757

Grant, M.J. & Booth, A. (2009). A typology of reviews: an analysis of the 14 review types and associated methodologies.  Health Information & Libraries Journal , 26(2), 91-108. https://www.doi.org/10.1111/j.1471-1842.2009.00848.x

Developed and refined by the Evidence for Policy and Practice Information and Co-ordinating Centre (EPPI-Centre), this review "map[s] out and categorize[s] existing literature on a particular topic, identifying gaps in research literature from which to commission further reviews and/or primary research" (Grant & Booth, 2009, p. 97).

Although mapping reviews are sometimes called scoping reviews, the key difference is that mapping reviews focus on a review question, rather than a topic

Mapping reviews are "best used where a clear target for a more focused evidence product has not yet been identified" (Booth, 2016, p. 14)

Mapping review searches are often quick and are intended to provide a broad overview

Mapping reviews can take different approaches in what types of literature is focused on in the search

Cooper I. D. (2016). What is a "mapping study?".  Journal of the Medical Library Association: JMLA ,  104 (1), 76–78. https://doi.org/10.3163/1536-5050.104.1.013

Miake-Lye, I. M., Hempel, S., Shanman, R., & Shekelle, P. G. (2016). What is an evidence map? A systematic review of published evidence maps and their definitions, methods, and products.  Systematic reviews, 5 (1), 1-21.  https://doi.org/10.1186/s13643-016-0204-x

Tainio, M., Andersen, Z. J., Nieuwenhuijsen, M. J., Hu, L., De Nazelle, A., An, R., ... & de Sá, T. H. (2021). Air pollution, physical activity and health: A mapping review of the evidence.  Environment international ,  147 , 105954.  https://doi.org/10.1016/j.envint.2020.105954

Booth, A. (2016). EVIDENT Guidance for Reviewing the Evidence: a compendium of methodological literature and websites . ResearchGate. https://doi.org/10.13140/RG.2.1.1562.9842 . 

Grant, M.J. & Booth, A. (2009). A typology of reviews: an analysis of the 14 review types and associated methodologies.  Health Information & Libraries Journal , 26(2), 91-108.  https://www.doi.org/10.1111/j.1471-1842.2009.00848.x

"A type of review that has as its primary objective the identification of the size and quality of research in a topic area in order to inform subsequent review" (Booth et al., 2012, p. 269).

  • Main purpose is to map out and categorize existing literature, identify gaps in literature—great for informing policy-making
  • Search comprehensiveness determined by time/scope constraints, could take longer than a systematic review
  • No formal quality assessment or critical appraisal

Learn more about the methods :

Arksey, H., & O'Malley, L. (2005) Scoping studies: towards a methodological framework.  International Journal of Social Research Methodology ,  8 (1), 19-32.  https://doi.org/10.1080/1364557032000119616

Levac, D., Colquhoun, H., & O’Brien, K. K. (2010). Scoping studies: Advancing the methodology. Implementation Science: IS, 5, 69. https://doi.org/10.1186/1748-5908-5-69

Example : 

Rahman, A., Sarkar, A., Yadav, O. P., Achari, G., & Slobodnik, J. (2021). Potential human health risks due to environmental exposure to nano-and microplastics and knowledge gaps: A scoping review.  Science of the Total Environment, 757 , 143872.  https://doi.org/10.1016/j.scitotenv.2020.143872

A review that "[compiles] evidence from multiple...reviews into one accessible and usable document" (Grant & Booth, 2009, p. 103). While originally intended to be a compilation of Cochrane reviews, it now generally refers to any kind of evidence synthesis.

  • Compiles evidence from multiple reviews into one document
  • Often defines a broader question than is typical of a traditional systematic review

Choi, G. J., & Kang, H. (2022). The umbrella review: a useful strategy in the rain of evidence.  The Korean Journal of Pain ,  35 (2), 127–128.  https://doi.org/10.3344/kjp.2022.35.2.127

Aromataris, E., Fernandez, R., Godfrey, C. M., Holly, C., Khalil, H., & Tungpunkom, P. (2015). Summarizing systematic reviews: Methodological development, conduct and reporting of an umbrella review approach. International Journal of Evidence-Based Healthcare , 13(3), 132–140. https://doi.org/10.1097/XEB.0000000000000055

Rojas-Rueda, D., Morales-Zamora, E., Alsufyani, W. A., Herbst, C. H., Al Balawi, S. M., Alsukait, R., & Alomran, M. (2021). Environmental risk factors and health: An umbrella review of meta-analyses.  International Journal of Environmental Research and Public Dealth ,  18 (2), 704.  https://doi.org/10.3390/ijerph18020704

A meta-analysis is a "technique that statistically combines the results of quantitative studies to provide a more precise effect of the result" (Grant & Booth, 2009, p. 98).

  • Statistical technique for combining results of quantitative studies to provide more precise effect of results
  • Aims for exhaustive, comprehensive searching
  • Quality assessment may determine inclusion/exclusion criteria
  • May be conducted independently or as part of a systematic review

Berman, N. G., & Parker, R. A. (2002). Meta-analysis: Neither quick nor easy. BMC Medical Research Methodology , 2(1), 10. https://doi.org/10.1186/1471-2288-2-10

Hites R. A. (2004). Polybrominated diphenyl ethers in the environment and in people: a meta-analysis of concentrations.  Environmental Science & Technology ,  38 (4), 945–956.  https://doi.org/10.1021/es035082g

A systematic review "seeks to systematically search for, appraise, and [synthesize] research evidence, often adhering to the guidelines on the conduct of a review" provided by discipline-specific organizations, such as the Cochrane Collaboration (Grant & Booth, 2009, p. 102).

  • Aims to compile and synthesize all known knowledge on a given topic
  • Adheres to strict guidelines, protocols, and frameworks
  • Time-intensive and often takes months to a year or more to complete
  • The most commonly referred to type of evidence synthesis. Sometimes confused as a blanket term for other types of reviews

Gascon, M., Triguero-Mas, M., Martínez, D., Dadvand, P., Forns, J., Plasència, A., & Nieuwenhuijsen, M. J. (2015). Mental health benefits of long-term exposure to residential green and blue spaces: a systematic review.  International Journal of Environmental Research and Public Health ,  12 (4), 4354–4379.  https://doi.org/10.3390/ijerph120404354

"Systematized reviews attempt to include one or more elements of the systematic review process while stopping short of claiming that the resultant output is a systematic review" (Grant & Booth, 2009, p. 102). When a systematic review approach is adapted to produce a more manageable scope, while still retaining the rigor of a systematic review such as risk of bias assessment and the use of a protocol, this is often referred to as a  structured review  (Huelin et al., 2015).

  • Typically conducted by postgraduate or graduate students
  • Often assigned by instructors to students who don't have the resources to conduct a full systematic review

Salvo, G., Lashewicz, B. M., Doyle-Baker, P. K., & McCormack, G. R. (2018). Neighbourhood built environment influences on physical activity among adults: A systematized review of qualitative evidence.  International Journal of Environmental Research and Public Health ,  15 (5), 897.  https://doi.org/10.3390/ijerph15050897

Huelin, R., Iheanacho, I., Payne, K., & Sandman, K. (2015). What’s in a name? Systematic and non-systematic literature reviews, and why the distinction matters. https://www.evidera.com/resource/whats-in-a-name-systematic-and-non-systematic-literature-reviews-and-why-the-distinction-matters/

Flowchart of review types

  • Review Decision Tree - Cornell University For more information, check out Cornell's review methodology decision tree.
  • LitR-Ex.com - Eight literature review methodologies Learn more about 8 different review types (incl. Systematic Reviews and Scoping Reviews) with practical tips about strengths and weaknesses of different methods.
  • << Previous: Getting started
  • Next: 1. Define your research question >>
  • Last Updated: Mar 21, 2024 11:32 AM
  • URL: https://guides.library.duke.edu/lit-reviews

Duke University Libraries

Services for...

  • Faculty & Instructors
  • Graduate Students
  • Undergraduate Students
  • International Students
  • Patrons with Disabilities

Twitter

  • Harmful Language Statement
  • Re-use & Attribution / Privacy
  • Support the Libraries

Creative Commons License

Have a language expert improve your writing

Run a free plagiarism check in 10 minutes, generate accurate citations for free.

  • Knowledge Base

Methodology

  • Systematic Review | Definition, Example, & Guide

Systematic Review | Definition, Example & Guide

Published on June 15, 2022 by Shaun Turney . Revised on November 20, 2023.

A systematic review is a type of review that uses repeatable methods to find, select, and synthesize all available evidence. It answers a clearly formulated research question and explicitly states the methods used to arrive at the answer.

They answered the question “What is the effectiveness of probiotics in reducing eczema symptoms and improving quality of life in patients with eczema?”

In this context, a probiotic is a health product that contains live microorganisms and is taken by mouth. Eczema is a common skin condition that causes red, itchy skin.

Table of contents

What is a systematic review, systematic review vs. meta-analysis, systematic review vs. literature review, systematic review vs. scoping review, when to conduct a systematic review, pros and cons of systematic reviews, step-by-step example of a systematic review, other interesting articles, frequently asked questions about systematic reviews.

A review is an overview of the research that’s already been completed on a topic.

What makes a systematic review different from other types of reviews is that the research methods are designed to reduce bias . The methods are repeatable, and the approach is formal and systematic:

  • Formulate a research question
  • Develop a protocol
  • Search for all relevant studies
  • Apply the selection criteria
  • Extract the data
  • Synthesize the data
  • Write and publish a report

Although multiple sets of guidelines exist, the Cochrane Handbook for Systematic Reviews is among the most widely used. It provides detailed guidelines on how to complete each step of the systematic review process.

Systematic reviews are most commonly used in medical and public health research, but they can also be found in other disciplines.

Systematic reviews typically answer their research question by synthesizing all available evidence and evaluating the quality of the evidence. Synthesizing means bringing together different information to tell a single, cohesive story. The synthesis can be narrative ( qualitative ), quantitative , or both.

Here's why students love Scribbr's proofreading services

Discover proofreading & editing

Systematic reviews often quantitatively synthesize the evidence using a meta-analysis . A meta-analysis is a statistical analysis, not a type of review.

A meta-analysis is a technique to synthesize results from multiple studies. It’s a statistical analysis that combines the results of two or more studies, usually to estimate an effect size .

A literature review is a type of review that uses a less systematic and formal approach than a systematic review. Typically, an expert in a topic will qualitatively summarize and evaluate previous work, without using a formal, explicit method.

Although literature reviews are often less time-consuming and can be insightful or helpful, they have a higher risk of bias and are less transparent than systematic reviews.

Similar to a systematic review, a scoping review is a type of review that tries to minimize bias by using transparent and repeatable methods.

However, a scoping review isn’t a type of systematic review. The most important difference is the goal: rather than answering a specific question, a scoping review explores a topic. The researcher tries to identify the main concepts, theories, and evidence, as well as gaps in the current research.

Sometimes scoping reviews are an exploratory preparation step for a systematic review, and sometimes they are a standalone project.

Prevent plagiarism. Run a free check.

A systematic review is a good choice of review if you want to answer a question about the effectiveness of an intervention , such as a medical treatment.

To conduct a systematic review, you’ll need the following:

  • A precise question , usually about the effectiveness of an intervention. The question needs to be about a topic that’s previously been studied by multiple researchers. If there’s no previous research, there’s nothing to review.
  • If you’re doing a systematic review on your own (e.g., for a research paper or thesis ), you should take appropriate measures to ensure the validity and reliability of your research.
  • Access to databases and journal archives. Often, your educational institution provides you with access.
  • Time. A professional systematic review is a time-consuming process: it will take the lead author about six months of full-time work. If you’re a student, you should narrow the scope of your systematic review and stick to a tight schedule.
  • Bibliographic, word-processing, spreadsheet, and statistical software . For example, you could use EndNote, Microsoft Word, Excel, and SPSS.

A systematic review has many pros .

  • They minimize research bias by considering all available evidence and evaluating each study for bias.
  • Their methods are transparent , so they can be scrutinized by others.
  • They’re thorough : they summarize all available evidence.
  • They can be replicated and updated by others.

Systematic reviews also have a few cons .

  • They’re time-consuming .
  • They’re narrow in scope : they only answer the precise research question.

The 7 steps for conducting a systematic review are explained with an example.

Step 1: Formulate a research question

Formulating the research question is probably the most important step of a systematic review. A clear research question will:

  • Allow you to more effectively communicate your research to other researchers and practitioners
  • Guide your decisions as you plan and conduct your systematic review

A good research question for a systematic review has four components, which you can remember with the acronym PICO :

  • Population(s) or problem(s)
  • Intervention(s)
  • Comparison(s)

You can rearrange these four components to write your research question:

  • What is the effectiveness of I versus C for O in P ?

Sometimes, you may want to include a fifth component, the type of study design . In this case, the acronym is PICOT .

  • Type of study design(s)
  • The population of patients with eczema
  • The intervention of probiotics
  • In comparison to no treatment, placebo , or non-probiotic treatment
  • The outcome of changes in participant-, parent-, and doctor-rated symptoms of eczema and quality of life
  • Randomized control trials, a type of study design

Their research question was:

  • What is the effectiveness of probiotics versus no treatment, a placebo, or a non-probiotic treatment for reducing eczema symptoms and improving quality of life in patients with eczema?

Step 2: Develop a protocol

A protocol is a document that contains your research plan for the systematic review. This is an important step because having a plan allows you to work more efficiently and reduces bias.

Your protocol should include the following components:

  • Background information : Provide the context of the research question, including why it’s important.
  • Research objective (s) : Rephrase your research question as an objective.
  • Selection criteria: State how you’ll decide which studies to include or exclude from your review.
  • Search strategy: Discuss your plan for finding studies.
  • Analysis: Explain what information you’ll collect from the studies and how you’ll synthesize the data.

If you’re a professional seeking to publish your review, it’s a good idea to bring together an advisory committee . This is a group of about six people who have experience in the topic you’re researching. They can help you make decisions about your protocol.

It’s highly recommended to register your protocol. Registering your protocol means submitting it to a database such as PROSPERO or ClinicalTrials.gov .

Step 3: Search for all relevant studies

Searching for relevant studies is the most time-consuming step of a systematic review.

To reduce bias, it’s important to search for relevant studies very thoroughly. Your strategy will depend on your field and your research question, but sources generally fall into these four categories:

  • Databases: Search multiple databases of peer-reviewed literature, such as PubMed or Scopus . Think carefully about how to phrase your search terms and include multiple synonyms of each word. Use Boolean operators if relevant.
  • Handsearching: In addition to searching the primary sources using databases, you’ll also need to search manually. One strategy is to scan relevant journals or conference proceedings. Another strategy is to scan the reference lists of relevant studies.
  • Gray literature: Gray literature includes documents produced by governments, universities, and other institutions that aren’t published by traditional publishers. Graduate student theses are an important type of gray literature, which you can search using the Networked Digital Library of Theses and Dissertations (NDLTD) . In medicine, clinical trial registries are another important type of gray literature.
  • Experts: Contact experts in the field to ask if they have unpublished studies that should be included in your review.

At this stage of your review, you won’t read the articles yet. Simply save any potentially relevant citations using bibliographic software, such as Scribbr’s APA or MLA Generator .

  • Databases: EMBASE, PsycINFO, AMED, LILACS, and ISI Web of Science
  • Handsearch: Conference proceedings and reference lists of articles
  • Gray literature: The Cochrane Library, the metaRegister of Controlled Trials, and the Ongoing Skin Trials Register
  • Experts: Authors of unpublished registered trials, pharmaceutical companies, and manufacturers of probiotics

Step 4: Apply the selection criteria

Applying the selection criteria is a three-person job. Two of you will independently read the studies and decide which to include in your review based on the selection criteria you established in your protocol . The third person’s job is to break any ties.

To increase inter-rater reliability , ensure that everyone thoroughly understands the selection criteria before you begin.

If you’re writing a systematic review as a student for an assignment, you might not have a team. In this case, you’ll have to apply the selection criteria on your own; you can mention this as a limitation in your paper’s discussion.

You should apply the selection criteria in two phases:

  • Based on the titles and abstracts : Decide whether each article potentially meets the selection criteria based on the information provided in the abstracts.
  • Based on the full texts: Download the articles that weren’t excluded during the first phase. If an article isn’t available online or through your library, you may need to contact the authors to ask for a copy. Read the articles and decide which articles meet the selection criteria.

It’s very important to keep a meticulous record of why you included or excluded each article. When the selection process is complete, you can summarize what you did using a PRISMA flow diagram .

Next, Boyle and colleagues found the full texts for each of the remaining studies. Boyle and Tang read through the articles to decide if any more studies needed to be excluded based on the selection criteria.

When Boyle and Tang disagreed about whether a study should be excluded, they discussed it with Varigos until the three researchers came to an agreement.

Step 5: Extract the data

Extracting the data means collecting information from the selected studies in a systematic way. There are two types of information you need to collect from each study:

  • Information about the study’s methods and results . The exact information will depend on your research question, but it might include the year, study design , sample size, context, research findings , and conclusions. If any data are missing, you’ll need to contact the study’s authors.
  • Your judgment of the quality of the evidence, including risk of bias .

You should collect this information using forms. You can find sample forms in The Registry of Methods and Tools for Evidence-Informed Decision Making and the Grading of Recommendations, Assessment, Development and Evaluations Working Group .

Extracting the data is also a three-person job. Two people should do this step independently, and the third person will resolve any disagreements.

They also collected data about possible sources of bias, such as how the study participants were randomized into the control and treatment groups.

Step 6: Synthesize the data

Synthesizing the data means bringing together the information you collected into a single, cohesive story. There are two main approaches to synthesizing the data:

  • Narrative ( qualitative ): Summarize the information in words. You’ll need to discuss the studies and assess their overall quality.
  • Quantitative : Use statistical methods to summarize and compare data from different studies. The most common quantitative approach is a meta-analysis , which allows you to combine results from multiple studies into a summary result.

Generally, you should use both approaches together whenever possible. If you don’t have enough data, or the data from different studies aren’t comparable, then you can take just a narrative approach. However, you should justify why a quantitative approach wasn’t possible.

Boyle and colleagues also divided the studies into subgroups, such as studies about babies, children, and adults, and analyzed the effect sizes within each group.

Step 7: Write and publish a report

The purpose of writing a systematic review article is to share the answer to your research question and explain how you arrived at this answer.

Your article should include the following sections:

  • Abstract : A summary of the review
  • Introduction : Including the rationale and objectives
  • Methods : Including the selection criteria, search method, data extraction method, and synthesis method
  • Results : Including results of the search and selection process, study characteristics, risk of bias in the studies, and synthesis results
  • Discussion : Including interpretation of the results and limitations of the review
  • Conclusion : The answer to your research question and implications for practice, policy, or research

To verify that your report includes everything it needs, you can use the PRISMA checklist .

Once your report is written, you can publish it in a systematic review database, such as the Cochrane Database of Systematic Reviews , and/or in a peer-reviewed journal.

In their report, Boyle and colleagues concluded that probiotics cannot be recommended for reducing eczema symptoms or improving quality of life in patients with eczema. Note Generative AI tools like ChatGPT can be useful at various stages of the writing and research process and can help you to write your systematic review. However, we strongly advise against trying to pass AI-generated text off as your own work.

If you want to know more about statistics , methodology , or research bias , make sure to check out some of our other articles with explanations and examples.

  • Student’s  t -distribution
  • Normal distribution
  • Null and Alternative Hypotheses
  • Chi square tests
  • Confidence interval
  • Quartiles & Quantiles
  • Cluster sampling
  • Stratified sampling
  • Data cleansing
  • Reproducibility vs Replicability
  • Peer review
  • Prospective cohort study

Research bias

  • Implicit bias
  • Cognitive bias
  • Placebo effect
  • Hawthorne effect
  • Hindsight bias
  • Affect heuristic
  • Social desirability bias

A literature review is a survey of scholarly sources (such as books, journal articles, and theses) related to a specific topic or research question .

It is often written as part of a thesis, dissertation , or research paper , in order to situate your work in relation to existing knowledge.

A literature review is a survey of credible sources on a topic, often used in dissertations , theses, and research papers . Literature reviews give an overview of knowledge on a subject, helping you identify relevant theories and methods, as well as gaps in existing research. Literature reviews are set up similarly to other  academic texts , with an introduction , a main body, and a conclusion .

An  annotated bibliography is a list of  source references that has a short description (called an annotation ) for each of the sources. It is often assigned as part of the research process for a  paper .  

A systematic review is secondary research because it uses existing research. You don’t collect new data yourself.

Cite this Scribbr article

If you want to cite this source, you can copy and paste the citation or click the “Cite this Scribbr article” button to automatically add the citation to our free Citation Generator.

Turney, S. (2023, November 20). Systematic Review | Definition, Example & Guide. Scribbr. Retrieved March 21, 2024, from https://www.scribbr.com/methodology/systematic-review/

Is this article helpful?

Shaun Turney

Shaun Turney

Other students also liked, how to write a literature review | guide, examples, & templates, how to write a research proposal | examples & templates, what is critical thinking | definition & examples, "i thought ai proofreading was useless but..".

I've been using Scribbr for years now and I know it's a service that won't disappoint. It does a good job spotting mistakes”

University Libraries

Literature review process.

  • Introduction
  • Video Tutorials
  • Select a Topic

Select a Review Type

Narrative/traditional literature review, scoping review, systematic review, meta-analysis, books about literature reviews.

  • Search the Literature
  • Plan Before Reviewing
  • Review the Literature
  • Write the Review

Before you start a literature review, you must determine the type of review you need to conduct for your project. Your choice will be influenced by your discipline and the purpose of the review. This page introduces you to four types of literature reviews and recommends resources about and examples of the reviews. The rest of this literature review guide provides general information that applies to most kinds of reviews.

For overviews of all review types, see these readings:

  • Typology of Literature Reviews A table from Chapter 9 of Handbook of eHealth Evaluation, 2017.
  • A Typology of Reviews: An Analysis of 14 Review Types and Associated Methodologies A 2009 article from Health Information and Libraries Journal by Grant and Booth.
  • Writing integrative literature reviews: Using the past and present to explore the future A 2016 article describing characteristics that should be found in all good literature reviews, regardless of type. Authored by Richard J. Torraco and published in Human Resource Development Review.

Characteristics:

  • Most common type of literature review and used in all disciplines; most frequently a section in a book/article/dissertation/thesis, but can also be a standalone review.
  • A selective and critical review of the most important literature related to your research question or hypothesis; creates context for your work and identifies the gaps in knowledge where you can contribute to the scholarly conversation.
  • Discussion of the literature may be thematic, methodological, or conceptual, but a chronological treatment is discouraged because it tends to become a summary rather than an evaluation of the literature. 
  • Am I the Only One Struggling to Write a Lit Review? 11 minute video from Sage Research Methods.
  • Literature Review Chapter 7 from Understanding and Evaluating Research: A Critical Guide by Sue L. T. McGregor, 2018.
  • Fostering Research and Publication in Academic Libraries Example of a Literature Review section on p. 459; Sassen and Wahl, 2014, College and Research Libraries
  • Radical Women in the Struggle: A Review of Recent Literature on the Civil Rights and Black Freedom Movements Example of a standalone review; Charon, 2013, Journal of Feminist Studies in Religion

Database

  • A review type mainly used in the social sciences and sciences; usually seen as a standalone review article.
  • Conducted to determine the scope and coverage of literature on a topic; the methods and sources for gathering the literature are made transparent so that the review can be reproduced. 
  • The review identifies definitions and concepts in a field, methods used, and gaps in knowledge; the results are often communicated through tables. 
  • Scoping Studies: Towards a Methodological Framework The article that introduced the framework for conducting scoping reviews by Arksey and O'Malley, 2005, International Journal of Social Research Methodology
  • Systematic Review or Scoping Review? Wondering which type of review to do? Read this 2018 article by Munn et al. from the journal, BMC Medical Research Methodology.
  • African Immigrant Women’s Experience in Western Host Societies: A Scoping Review Okeke-Ihejirika et al., 2018, Journal of Gender Studies
  • A Scoping Review of Mentoring Programs for Academic Librarians Lorenzetti and Powelson, 2015, Journal of Academic Librarianship

For much more information about systematic reviews, visit our Systematic Reviews guide .

  • A review type that originated in medicine ( Cochrane Reviews ) and has since been adopted by other health sciences and social sciences ( Campbell Collaboration ); published as a standalone article.
  • The review synthesizes knowledge from multiple studies concerning a focused research question and provides an evidence-based conclusion; considered one of the most reliable sources of evidence in medicine.
  • Uses transparent criteria for including/excluding literature based on quality. 
  • Disciplines have standardized guidelines for conducting and reporting reviews - see Resources.
  • Often done by a team composed of experts from the field, information science, and statistics.
  • Synthesizing Evidence: Systematic Reviews, Meta-Analysis and Preference Analysis Find an overview of systematic reviews and meta-analyses in Chapter 11 from Research Methods for Clinical and Health Psychology by Marks and Yancey, 2004. For further reading, see the Bibliography of this ebook.
  • How to Do a Systematic Review: A Best Practice Guide for Conducting and Reporting Narrative Reviews, Meta-Analyses, and Meta-Syntheses A 2019 article in Annual Review of Psychology by Siddaway et al.
  • Cochrane Handbook for Systematic Reviews of Interventions, Second Edition The official handbook for conducting systematic reviews of interventions in the health sciences.
  • PRISMA: Preferred Reporting Items for Systematic Reviews and Meta-Analyses Highly recommended guidelines for producing transparent systematic reviews and meta-analyses when evaluating randomized clinical trials and interventions; the PRISMA approach is required by some journals.
  • Self-management interventions for reducing challenging behaviors among school-age students: A systematic review A 2022 article from Campbell Systematic Reviews by Smith et al.
  • The characteristics of effective technology-enabled dementia education: a systematic review and mixed research synthesis A 2022 article by Muirhead et al. from BMC Systematic Reviews.
  • Campbell Systematic Reviews See this open access journal from the Campbell Collaboration for examples of systematic reviews in the social sciences.
  • Systematic Reviews, BioMed Central See this open access journal for examples of systematic reviews in health sciences.
  • A review type that originated in medicine ( Cochrane Reviews ) and has since been adopted by other health sciences and social sciences ( Campbell Collaboration ); published as a standalone article or in combination with a systematic review (see box above).
  • The review synthesizes the results of multiple studies using statistics to provide an evidence-based answer to a research question; considered one of the most reliable sources of evidence in medicine.
  • Knowledge in application of statistics is required.
  • Methods of Meta-analysis: Correcting Error and Bias in Research Findings A comprehensive ebook on meta-analyses by Schmidt and Hunter, 2015.
  • Genetic Meta-analysis of Diagnosed Alzheimer's Disease Identifies New Risk Loci and Implicates A Beta, Tau, Immunity and Lipid Processing Kunkle et al., 2019, Nature Genetics
  • Research on Religion/Spirituality and Forgiveness: A Meta-analytic Review Davis et al., 2013, Psychology of Religion and Spirituality
  • Campbell Systematic Reviews See this open access journal from the Campbell Collaboration for examples of meta-analyses in the social sciences.
  • Systematic Reviews, BioMed Central See this open access journal for examples of meta-analyses in health sciences.

Cover Art

Need help? Then use the library's  Ask Us service. Get help from real people face-to-face, by phone, or by email.

Ask Us!

  • << Previous: Select a Topic
  • Next: Search the Literature >>
  • Last Updated: Nov 13, 2023 4:28 PM
  • URL: https://guides.library.unt.edu/literature-review

Additional Links

UNT: Apply now UNT: Schedule a tour UNT: Get more info about the University of North Texas

UNT: Disclaimer | UNT: AA/EOE/ADA | UNT: Privacy | UNT: Electronic Accessibility | UNT: Required Links | UNT: UNT Home

Log in using your username and password

  • Search More Search for this keyword Advanced search
  • Latest content
  • Current issue
  • Write for Us
  • BMJ Journals More You are viewing from: Google Indexer

You are here

  • Volume 24, Issue 2
  • Five tips for developing useful literature summary tables for writing review articles
  • Article Text
  • Article info
  • Citation Tools
  • Rapid Responses
  • Article metrics

Download PDF

  • http://orcid.org/0000-0003-0157-5319 Ahtisham Younas 1 , 2 ,
  • http://orcid.org/0000-0002-7839-8130 Parveen Ali 3 , 4
  • 1 Memorial University of Newfoundland , St John's , Newfoundland , Canada
  • 2 Swat College of Nursing , Pakistan
  • 3 School of Nursing and Midwifery , University of Sheffield , Sheffield , South Yorkshire , UK
  • 4 Sheffield University Interpersonal Violence Research Group , Sheffield University , Sheffield , UK
  • Correspondence to Ahtisham Younas, Memorial University of Newfoundland, St John's, NL A1C 5C4, Canada; ay6133{at}mun.ca

https://doi.org/10.1136/ebnurs-2021-103417

Statistics from Altmetric.com

Request permissions.

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.

Introduction

Literature reviews offer a critical synthesis of empirical and theoretical literature to assess the strength of evidence, develop guidelines for practice and policymaking, and identify areas for future research. 1 It is often essential and usually the first task in any research endeavour, particularly in masters or doctoral level education. For effective data extraction and rigorous synthesis in reviews, the use of literature summary tables is of utmost importance. A literature summary table provides a synopsis of an included article. It succinctly presents its purpose, methods, findings and other relevant information pertinent to the review. The aim of developing these literature summary tables is to provide the reader with the information at one glance. Since there are multiple types of reviews (eg, systematic, integrative, scoping, critical and mixed methods) with distinct purposes and techniques, 2 there could be various approaches for developing literature summary tables making it a complex task specialty for the novice researchers or reviewers. Here, we offer five tips for authors of the review articles, relevant to all types of reviews, for creating useful and relevant literature summary tables. We also provide examples from our published reviews to illustrate how useful literature summary tables can be developed and what sort of information should be provided.

Tip 1: provide detailed information about frameworks and methods

  • Download figure
  • Open in new tab
  • Download powerpoint

Tabular literature summaries from a scoping review. Source: Rasheed et al . 3

The provision of information about conceptual and theoretical frameworks and methods is useful for several reasons. First, in quantitative (reviews synthesising the results of quantitative studies) and mixed reviews (reviews synthesising the results of both qualitative and quantitative studies to address a mixed review question), it allows the readers to assess the congruence of the core findings and methods with the adapted framework and tested assumptions. In qualitative reviews (reviews synthesising results of qualitative studies), this information is beneficial for readers to recognise the underlying philosophical and paradigmatic stance of the authors of the included articles. For example, imagine the authors of an article, included in a review, used phenomenological inquiry for their research. In that case, the review authors and the readers of the review need to know what kind of (transcendental or hermeneutic) philosophical stance guided the inquiry. Review authors should, therefore, include the philosophical stance in their literature summary for the particular article. Second, information about frameworks and methods enables review authors and readers to judge the quality of the research, which allows for discerning the strengths and limitations of the article. For example, if authors of an included article intended to develop a new scale and test its psychometric properties. To achieve this aim, they used a convenience sample of 150 participants and performed exploratory (EFA) and confirmatory factor analysis (CFA) on the same sample. Such an approach would indicate a flawed methodology because EFA and CFA should not be conducted on the same sample. The review authors must include this information in their summary table. Omitting this information from a summary could lead to the inclusion of a flawed article in the review, thereby jeopardising the review’s rigour.

Tip 2: include strengths and limitations for each article

Critical appraisal of individual articles included in a review is crucial for increasing the rigour of the review. Despite using various templates for critical appraisal, authors often do not provide detailed information about each reviewed article’s strengths and limitations. Merely noting the quality score based on standardised critical appraisal templates is not adequate because the readers should be able to identify the reasons for assigning a weak or moderate rating. Many recent critical appraisal checklists (eg, Mixed Methods Appraisal Tool) discourage review authors from assigning a quality score and recommend noting the main strengths and limitations of included studies. It is also vital that methodological and conceptual limitations and strengths of the articles included in the review are provided because not all review articles include empirical research papers. Rather some review synthesises the theoretical aspects of articles. Providing information about conceptual limitations is also important for readers to judge the quality of foundations of the research. For example, if you included a mixed-methods study in the review, reporting the methodological and conceptual limitations about ‘integration’ is critical for evaluating the study’s strength. Suppose the authors only collected qualitative and quantitative data and did not state the intent and timing of integration. In that case, the strength of the study is weak. Integration only occurred at the levels of data collection. However, integration may not have occurred at the analysis, interpretation and reporting levels.

Tip 3: write conceptual contribution of each reviewed article

While reading and evaluating review papers, we have observed that many review authors only provide core results of the article included in a review and do not explain the conceptual contribution offered by the included article. We refer to conceptual contribution as a description of how the article’s key results contribute towards the development of potential codes, themes or subthemes, or emerging patterns that are reported as the review findings. For example, the authors of a review article noted that one of the research articles included in their review demonstrated the usefulness of case studies and reflective logs as strategies for fostering compassion in nursing students. The conceptual contribution of this research article could be that experiential learning is one way to teach compassion to nursing students, as supported by case studies and reflective logs. This conceptual contribution of the article should be mentioned in the literature summary table. Delineating each reviewed article’s conceptual contribution is particularly beneficial in qualitative reviews, mixed-methods reviews, and critical reviews that often focus on developing models and describing or explaining various phenomena. Figure 2 offers an example of a literature summary table. 4

Tabular literature summaries from a critical review. Source: Younas and Maddigan. 4

Tip 4: compose potential themes from each article during summary writing

While developing literature summary tables, many authors use themes or subthemes reported in the given articles as the key results of their own review. Such an approach prevents the review authors from understanding the article’s conceptual contribution, developing rigorous synthesis and drawing reasonable interpretations of results from an individual article. Ultimately, it affects the generation of novel review findings. For example, one of the articles about women’s healthcare-seeking behaviours in developing countries reported a theme ‘social-cultural determinants of health as precursors of delays’. Instead of using this theme as one of the review findings, the reviewers should read and interpret beyond the given description in an article, compare and contrast themes, findings from one article with findings and themes from another article to find similarities and differences and to understand and explain bigger picture for their readers. Therefore, while developing literature summary tables, think twice before using the predeveloped themes. Including your themes in the summary tables (see figure 1 ) demonstrates to the readers that a robust method of data extraction and synthesis has been followed.

Tip 5: create your personalised template for literature summaries

Often templates are available for data extraction and development of literature summary tables. The available templates may be in the form of a table, chart or a structured framework that extracts some essential information about every article. The commonly used information may include authors, purpose, methods, key results and quality scores. While extracting all relevant information is important, such templates should be tailored to meet the needs of the individuals’ review. For example, for a review about the effectiveness of healthcare interventions, a literature summary table must include information about the intervention, its type, content timing, duration, setting, effectiveness, negative consequences, and receivers and implementers’ experiences of its usage. Similarly, literature summary tables for articles included in a meta-synthesis must include information about the participants’ characteristics, research context and conceptual contribution of each reviewed article so as to help the reader make an informed decision about the usefulness or lack of usefulness of the individual article in the review and the whole review.

In conclusion, narrative or systematic reviews are almost always conducted as a part of any educational project (thesis or dissertation) or academic or clinical research. Literature reviews are the foundation of research on a given topic. Robust and high-quality reviews play an instrumental role in guiding research, practice and policymaking. However, the quality of reviews is also contingent on rigorous data extraction and synthesis, which require developing literature summaries. We have outlined five tips that could enhance the quality of the data extraction and synthesis process by developing useful literature summaries.

  • Aromataris E ,
  • Rasheed SP ,

Twitter @Ahtisham04, @parveenazamali

Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

Competing interests None declared.

Patient consent for publication Not required.

Provenance and peer review Not commissioned; externally peer reviewed.

Read the full text or download the PDF:

Advertisement

Advertisement

Characteristics of restricted interests in girls with ASD compared to boys: a systematic review of the literature

  • Published: 30 May 2022

Cite this article

  • Lise Bourson 1 &
  • Camille Prevost 2  

1537 Accesses

6 Citations

13 Altmetric

Explore all metrics

The existence of a female phenotype profile in autistic spectrum disorder is one of the current hypotheses to explain the diagnostic discrepancy between men and women. In this context, an international literature review was carried out to evidence and describe the characteristics of restricted interests found in girls with autistic spectrum disorder. A documentary search was conducted on PubMed and a systematic literature review was carried out based on the PRISMA methodology. We selected studies with a population of boys and girls diagnosed as autistic according to the DSM-IV or the DSM-5, in which quantitative and descriptive comparisons of restricted interests, according to gender were carried out. Nineteen studies were found to be relevant. Fifteen enabled a refining of the characteristics of restricted interests among females: fewer restricted interests were identified in comparison with boys, and the autistic girls’ interests seem to be closer to those of neurotypical girls than to those of autistic boys, which thus led to more complex screening. Age and Intelligence quotient seem to be two factors that trigger variations in restricted interests differently according to gender. Representations among professionals also have an impact on diagnoses among girls. For future research, one of the perspectives could be a comparison between girls with autism and neurotypical girls to limit gender bias. The present results contribute to potentially extending knowledge of a female phenotypical profile in autism and show the need to improve the general population’s awareness, to improve health professionals’ training and possibly to revise the diagnostic tools.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Price includes VAT (Russian Federation)

Instant access to the full article PDF.

Rent this article via DeepDyve

Institutional subscriptions

what are the characteristics of a literature review

Availability of data and material

Not applicable.

Code availability

Fombonne E (2009) Epidemiology of pervasive developmental disorders. Pediatr Res 65:591–598. https://doi.org/10.1203/PDR.0b013e31819e7203

Article   PubMed   Google Scholar  

Fombonne E (1999) The epidemiology of autism: a review. Psychol Med 29:769–786. https://doi.org/10.1017/S0033291799008508

Article   CAS   PubMed   Google Scholar  

AP Association [APA] (2000) Diagnostic and Statistical Manual of Mental Disorders, 4th edn. APA, Washington, D.C.

Google Scholar  

American Psychiatric Association (2013) Diagnostic and Statistical Manual of Mental Disorders, 5th edn. APA, Washington, D.C.

Book   Google Scholar  

DeLoache JS, Simcock G, Macari S (2007) Planes, trains, automobiles and tea sets: extremely intense interests in very young children. Dev Psychol 43:1579–1586. https://doi.org/10.1037/0012-1649.43.6.1579

Kim YS, Leventhal BL, Koh Y-J et al (2011) Prevalence of autism spectrum disorders in a total population sample. AJP 168:904–912. https://doi.org/10.1176/appi.ajp.2011.10101532

Article   Google Scholar  

Mattila M-L, Kielinen M, Linna S-L et al (2011) Autism spectrum disorders according to DSM-IV-TR and comparison with DSM-5 draft criteria: an epidemiological study. J Am Acad Child Adolesc Psychiatry 50:583-592.e11. https://doi.org/10.1016/j.jaac.2011.04.001

Kopp S, Gillberg C (1992) Girls with social deficits and learning problems: Autism, atypical Asperger syndrome or a variant of these conditions. Eur Child Adolesc Psychiatry 1:89–99. https://doi.org/10.1007/BF02091791

Kirkovski M, Enticott PG, Fitzgerald PB (2013) A review of the role of female gender in ASD. J Autism Dev Disord 43:2584–2603. https://doi.org/10.1007/s10803-013-1811-1

Dean M, Harwood R, Kasari C (2016) The art of camouflage: Gender differences in the social behaviors of girls and boys with autism spectrum disorder. Autism 21:678–689. https://doi.org/10.1177/1362361316671845

Bargiela S, Steward R, Mandy W (2016) The experiences of late-diagnosed women with autism spectrum conditions: an investigation of the female autism phenotype. J Autism Dev Disord 46:3281–3294. https://doi.org/10.1007/s10803-016-2872-8

Article   PubMed   PubMed Central   Google Scholar  

Young H, Oreve M-J, Speranza M (2018) Clinical characteristics and problems diagnosing autism spectrum disorder in girls. Arch Pediatr 25:399–403. https://doi.org/10.1016/j.arcped.2018.06.008

Van Wijngaarden-Cremers PJM, van Eeten E, Groen WB et al (2014) Gender and age differences in the core triad of impairments in autism spectrum disorders: a systematic review and meta-analysis. J Autism Dev Disord 44:627–635. https://doi.org/10.1007/s10803-013-1913-9

Allely C (2019) Exploring the female autism phenotype of repetitive behaviours and restricted interests (RBRIs): a systematic PRISMA review. Adv Autism 5:171–186. https://doi.org/10.1108/AIA-09-2018-0030

Leekam SR, Prior MR, Uljarevic M (2011) Restricted and repetitive behaviors in autism spectrum disorders: a review of research in the last decade. Psychol Bull 137:562–593. https://doi.org/10.1037/a0023341

Kreiser NL, White SW (2013) ASD in females: are we overstating the gender difference in diagnosis? Clin Child Fam Psychol Rev 17:67–84. https://doi.org/10.1007/s10567-013-0148-9

Lai M-C, Lombardo MV, Auyeung B et al (2015) Sex/gender differences and autism: setting the scene for future research. J Am Acad Child Adolesc Psychiatry 54:11–24. https://doi.org/10.1016/j.jaac.2014.10.003

PRISMA-P Group, Moher D, Shamseer L et al (2015) Preferred reporting items for systematic review and meta-analysis protocols (PRISMA-P) 2015 statement. Syst Rev 4:1. https://doi.org/10.1186/2046-4053-4-1

Article   PubMed Central   Google Scholar  

McFayden TC, Albright J, Muskett AE, Scarpa A (2018) Brief report: sex differences in asd diagnosis—a brief report on restricted interests and repetitive behaviors. J Autism Dev Disord 49:1693–1699. https://doi.org/10.1007/s10803-018-3838-9

Anthony LG, Kenworthy L, Yerys BE et al (2013) Interests in high-functioning autism are more intense, interfering, and idiosyncratic than those in neurotypical development. Dev Psychopathol 25:643–652. https://doi.org/10.1017/S0954579413000072

Nowell W, Jones DR, Harrop C (2018) Circumscribed interests in autism: are there sex differences? Adv Autism. https://doi.org/10.1108/AIA-09-2018-0032

Sutherland R, Hodge A, Bruck S et al (2017) Parent-reported differences between school-aged girls and boys on the autism spectrum. Autism 21:785–794. https://doi.org/10.1177/1362361316668653

Szatmari P, Liu X-Q, Goldberg J et al (2011) Sex differences in repetitive stereotyped behaviors in autism: implications for genetic liability. Am J Med Genet B Neuropsychiatr Genet 159B:5–12. https://doi.org/10.1002/ajmg.b.31238

Hiller RM, Young RL, Weber N (2014) Sex differences in autism spectrum disorder based on DSM-5 criteria: evidence from clinician and teacher reporting. J Abnorm Child Psychol 42:1381–1393. https://doi.org/10.1007/s10802-014-9881-x

Frazier TW, Georgiades S, Bishop SL, Hardan AY (2014) Behavioral and cognitive characteristics of females and males with autism in the Simons Simplex Collection. J Am Acad Child Adolesc Psychiatry 53(329–340):e1-3. https://doi.org/10.1016/j.jaac.2013.12.004

Fulceri F, Narzisi A, Apicella F et al (2015) Application of the Repetitive Behavior Scale-Revised – Italian version – in preschoolers with autism spectrum disorder. Res Dev Disabil 48:43–52. https://doi.org/10.1016/j.ridd.2015.10.015

Hiller RM, Young RL, Weber N (2015) Sex differences in pre-diagnosis concerns for children later diagnosed with autism spectrum disorder. Autism 20:75–84. https://doi.org/10.1177/1362361314568899

Frazier TW, Hardan AY (2016) Equivalence of symptom dimensions in females and males with autism. Autism 21:749–759. https://doi.org/10.1177/1362361316660066

Beggiato A, Peyre H, Maruani A et al (2016) Gender differences in autism spectrum disorders: divergence among specific core symptoms: gender differences in ASD. Autism Res 10:680–689. https://doi.org/10.1002/aur.1715

Antezana L, Factor RS, Condy EE et al (2018) Gender differences in restricted and repetitive behaviors and interests in youth with autism. Autism Res 12:274–283. https://doi.org/10.1002/aur.2049

Nicholas JS, Charles JM, Carpenter LA et al (2008) Prevalence and characteristics of children with autism-spectrum disorders. Ann Epidemiol 18:130–136. https://doi.org/10.1016/j.annepidem.2007.10.013

Wang S, Deng H, You C et al (2017) Sex differences in diagnosis and clinical phenotypes of Chinese children with autism spectrum disorder. Neurosci Bull 33:153–160. https://doi.org/10.1007/s12264-017-0102-9

Jamison R, Bishop SL, Huerta M, Halladay AK (2017) The clinician perspective on sex differences in autism spectrum disorders. Autism 21:772–784. https://doi.org/10.1177/1362361316681481

Knutsen J, Crossman M, Perrin J et al (2019) Sex differences in restricted repetitive behaviors and interests in children with autism spectrum disorder: an Autism Treatment Network study. Autism 23:858–868. https://doi.org/10.1177/1362361318786490

Mayes SD, Calhoun SL (2010) Impact of IQ, age, SES, gender, and race on autistic symptoms. Res Autism Spectrum Disord 5:749–757. https://doi.org/10.1016/j.rasd.2010.09.002

Solomon M, Miller M, Taylor SL et al (2011) Autism symptoms and internalizing psychopathology in girls and boys with autism spectrum disorders. J Autism Dev Disord 42:48–59. https://doi.org/10.1007/s10803-011-1215-z

Uljarević M, Cooper MN, Bebbington K et al (2020) Deconstructing the repetitive behaviour phenotype in autism spectrum disorder through a large population-based analysis. J Child Psychol Psychiatr. https://doi.org/10.1111/jcpp.13203

Seltzer MM, Shattuck P, Abbeduto L, Greenberg JS (2004) Trajectory of development in adolescents and adults with autism. Ment Retard Dev Disabil Res Rev 10:234–247. https://doi.org/10.1002/mrdd.20038

Gould J, Ashton-Smith J (2011) Missed diagnosis or misdiagnosis? Girls and women on the autism spectrum. Good Autism Practice (GAP) 12(8):34–41

Bodfish JW (2003) Interests Scale. Chapel Hill, NC

Gould J (2017) Towards understanding the under-recognition of girls and women on the autism spectrum. Autism 21:703–705. https://doi.org/10.1177/1362361317706174

Duvekot J, van der Ende J, Verhulst FC et al (2016) Factors influencing the probability of a diagnosis of autism spectrum disorder in girls versus boys. Autism 21:646–658. https://doi.org/10.1177/1362361316672178

Attwood T, Garnett MS, Rynkiewicz A GQ-ASC (Girls’ Questionnaire for Autism Spectrum Conditions) [Measurement instrument]

Hull L, Petrides KV, Allison C et al (2017) “Putting on My Best Normal”: Social Camouflaging in Adults with Autism Spectrum Conditions. J Autism Dev Disord 47:2519–2534. https://doi.org/10.1007/s10803-017-3166-5

Sasson NJ, Faso DJ, Nugent J et al (2017) Neurotypical peers are less willing to interact with those with autism based on thin slice judgments. Sci Rep 7:40700. https://doi.org/10.1038/srep40700

Article   CAS   PubMed   PubMed Central   Google Scholar  

May T, Cornish K, Rinehart NJ (2012) Gender profiles of behavioral attention in children with autism spectrum disorder. J Atten Disord 20:627–635. https://doi.org/10.1177/1087054712455502

Crijnen AAM, Achenbach TM, Verhulst FC (1997) Comparisons of problems reported by parents of children in 12 cultures: total problems, externalizing, and internalizing. J Am Acad Child Adolesc Psychiatry 36:1269–1277. https://doi.org/10.1097/00004583-199709000-00020

Holtmann M, Bölte S, Poustka F (2007) Autism spectrum disorders: sex differences in autistic behaviour domains and coexisting psychopathology. Dev Med Child Neurol 49:361–366. https://doi.org/10.1111/j.1469-8749.2007.00361.x

Giarelli E, Wiggins LD, Rice CE et al (2010) Sex differences in the evaluation and diagnosis of autism spectrum disorders among children. Disabil Health J 3:107–116. https://doi.org/10.1016/j.dhjo.2009.07.001

Dworzynski K, Ronald A, Bolton P, Happé F (2012) How different are girls and boys above and below the diagnostic threshold for autism spectrum disorders? J Am Acad Child Adolesc Psychiatry 51:788–797. https://doi.org/10.1016/j.jaac.2012.05.018

Russell G, Steer C, Golding J (2010) Social and demographic factors that influence the diagnosis of autistic spectrum disorders. Soc Psychiatry Psychiatr Epidemiol 46:1283–1293. https://doi.org/10.1007/s00127-010-0294-z

Shattuck PT, Durkin M, Maenner M et al (2009) Timing of identification among children with an autism spectrum disorder: findings from a population-based surveillance study. J Am Acad Child Adolesc Psychiatry 48:474–483. https://doi.org/10.1097/CHI.0b013e31819b3848

Hirt ER (1990) Do I see only what I expect? Evidence for an expectancy-guided retrieval model. J Pers Soc Psychol 58:937–951. https://doi.org/10.1037/0022-3514.58.6.937

Download references

No funding was received to assist with the preparation of this manuscript.

Author information

Authors and affiliations.

The Université de Paris, Paris, France

Lise Bourson

Université Paris Saclay - CESP INSERM U1178, CCU-AH at the Centre Hospitalier Fondation Vallée, Gentilly, France

Camille Prevost

You can also search for this author in PubMed   Google Scholar

Corresponding author

Correspondence to Lise Bourson .

Ethics declarations

Conflict of interest.

The authors declare they have no conflict of interest.

Rights and permissions

Reprints and permissions

About this article

Bourson, L., Prevost, C. Characteristics of restricted interests in girls with ASD compared to boys: a systematic review of the literature. Eur Child Adolesc Psychiatry (2022). https://doi.org/10.1007/s00787-022-01998-5

Download citation

Received : 12 July 2021

Accepted : 23 April 2022

Published : 30 May 2022

DOI : https://doi.org/10.1007/s00787-022-01998-5

Share this article

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

  • Autistic spectrum disorder
  • Restricted interests
  • Circumscribed interests
  • Find a journal
  • Publish with us
  • Track your research
  • Search Menu
  • Advance articles
  • Collections
  • Editor's Choice
  • Supplements
  • Author Guidelines
  • Submission Site
  • Open Access
  • About Journal of Travel Medicine
  • About the International Society of Travel Medicine
  • Editorial Board
  • Advertising and Corporate Services
  • Journals Career Network
  • Self-Archiving Policy
  • Journals on Oxford Academic
  • Books on Oxford Academic

International Society of Travel Medicine

Article Contents

  • Author contributions
  • Conflict of interest
  • < Previous

Characteristics of possible mpox reinfection cases: literature review

Stefano Musumeci and Jérôme Laflamme contributed equally to this work

  • Article contents
  • Figures & tables
  • Supplementary Data

Stefano Musumeci, Jérôme Laflamme, Laurent Kaiser, Olivier Segeral, Alexandra Calmy, Characteristics of possible mpox reinfection cases: literature review, Journal of Travel Medicine , Volume 30, Issue 7, October 2023, taad136, https://doi.org/10.1093/jtm/taad136

  • Permissions Icon Permissions

As of September 2023, >90 000 confirmed mpox cases 1 have been reported in 110 countries since the beginning of the worldwide outbreak. In the context of the ongoing outbreak, monkeypox virus (MPXV) is almost exclusively transmitted through intimate skin-to-skin contact, most often through sexual activity. 2 Infection caused by MPXV is expected to provide long-term protection against reinfection but data on cellular and humoral post-infectious immunity are scarce. 2

Since January 2023, 16 cases of possible mpox reinfection ( Table 1) have been reported. Among those cases, eight were case-reports and eight were recently described in a global case-series by Hazra et al . 4 Reinfection was considered possible if the patient presented with a second distinct episode of mpox, confirmed by the presence of MPXV on polymerase chain reaction (PCR) analysis, after clinical resolution of the first episode. Whole-genome sequencing of both MPXV infections was only successful in one case. 3 All the putative cases happened in males, aged between 27 and 51 years old, who self-identified as men who have sex with men. The time between mpox episodes varied from less than one month to almost a year. Eight individuals used HIV pre-exposure prophylaxis and eight were living with HIV (PLWH) with an immunovirological control under antiretroviral therapy. Ten had bacterial sexually transmitted diseases (STDs) concomitant to the second mpox episode and most of them reported having had multiple sexual partners in the days or weeks before. Two were vaccinated with two doses of modified Ankara Vaccine (MVA) between the two mpox episodes and one was vaccinated against smallpox during childhood. All cases presented with non-severe symptoms, and none needed hospitalization or specific antiviral treatment for mpox. Information on sexual partners, including HIV status, is lacking.

  • reinfection

Email alerts

More on this topic, related articles in pubmed, citing articles via.

  • Recommend to your Library

Affiliations

  • Online ISSN 1708-8305
  • Copyright © 2024 International Society of Travel Medicine
  • About Oxford Academic
  • Publish journals with us
  • University press partners
  • What we publish
  • New features  
  • Open access
  • Institutional account management
  • Rights and permissions
  • Get help with access
  • Accessibility
  • Advertising
  • Media enquiries
  • Oxford University Press
  • Oxford Languages
  • University of Oxford

Oxford University Press is a department of the University of Oxford. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide

  • Copyright © 2024 Oxford University Press
  • Cookie settings
  • Cookie policy
  • Privacy policy
  • Legal notice

This Feature Is Available To Subscribers Only

Sign In or Create an Account

This PDF is available to Subscribers Only

For full access to this pdf, sign in to an existing account, or purchase an annual subscription.

SYSTEMATIC REVIEW article

The effect of scutellaria baicalensis and its active ingredients on major depressive disorder: a systematic review and meta-analysis of literature in pre-clinical research.

Ying Ma&#x;

  • 1 Department of Pharmacy, Changzheng Hospital, Second Military Medical University, Shanghai, China
  • 2 Institute of Chinese Materia Madica, Shanghai University of Traditional Chinese Medicine, Shanghai, China

Background: Scutellaria baicalensis, the dry root of scutellaria baicalensis georgi, is a traditional Chinese medicine with long. In clinic, scutellaria baicalensis is commonly used in prescription for the treatment of depression. Additionally, numerous pre-clinical studies have shown that Scutellaria baicalensis and its active constituents are effective for depression. In this study, we aims to systematically review the roles of scutellaria baicalensis in depression and summarize the possible mechanism.

Methods: A systematic review and meta-analysis were conducted to analyze the existing studies on the effects of scutellaria baicalensis on depression in animal models. Briefly, we searched electronic databases including Pubmed and Embase for preclinical trial studies from inception to September 2023. The items in each study were evaluated by two independent reviewers, and meta-analyses were performed on scutellaria baicalensis-induced behavioral changes in the study. Finally, random effects model is used to collect data.

Results: A total of 49 studies were identified, and 13 studies were included in the final analysis. They all reported the different antidepressant effects of scutellaria baicalensis and the underlying biological mechanisms. Among the included 13 studies, the results of eight articles SPT[SMD = −2.80, 95%CI(-4.03, -1.57), p < 0.01], the results of the nine articles OFT[SMD = −2.38, 95%CI(-3.53, -1.23), p < 0.01], and the results of two articles NSFT[SMD = −2.98, 95%CI(-3.94, -2.02), p < 0.01] were significantly different from the control group. The risk of bias was moderate in all studies, however, there was a significant heterogeneity among studies.

Conclusion: These results preliminarily suggest that scutellaria baicalensis can alleviate depressive behaviors and modulate underlying mechanisms, which is expected to be a promising antidepressant.

1 Introduction

Depression (major depressive disorder), a common mental disease, is manifested by persistent feeling of sadness and loss of interest. This kind of disease can disturb person’s ability to work, study, sleep, eat, and enjoy once pleasurable activities. What’s more, people with depression possess cognitive behavioral, social dysfunction, and even suicide tendency in severe cases ( Vos et al., 2017 ; Dwyer Jennifer et al., 2020 ). In recent years, its commonly defined that depression is global burden of disease with high mortality and morbidity, and high disability rate. In America, In 2017, the World Health Organization revealed that there were more than 300 million depression patients in the world, accounting for about 4.4% of the global population ( World Health Organization WHO, 2017 ). Depression accounts for a large share of the global disease burden, with approximately 264 million people globally estimated to suffer from the condition ( World Health Organization (WHO) ). In China, a cross-sectional epidemiological study from 2013.07 to 2015.03 revealed that the economic burden of China is about 2.5 trillion US dollars, accounting for 10% of the total global disease burden ( Jin et al., 2021 ). A cross-national comparison reported that lifetime prevalence estimates of major depressive disorders ranged from 1.0% (Czech Republic) to 16.9% (United States), with midpoints at 8.3% (Canada) and 9.0% (Chile), while the 12-month prevalence estimates ranged from 0.3% (Czech Republic) to 10% (United States), with midpoints at 4.5% (Mexico) and 5.2% (West Germany) ( Kessler Ronald and Bromet Evelyn, 2013 ). Another cross-sectional survey analysis conducted in USA also pointed that individuals with depression diagnosis have substantial humanistic and economic burden ( Jain et al., 2022 ). In 2015, The World Health Organization ranked depression as the single largest contributor to global disability, accounting for 7.5% of all years lived with disability ( World Health Organization WHO, 2017 ). These epidemiological studies highlight that depressive disorder is a current issue for public health and will be a future challenge.

More and more studies on depression have shown that numerous factors, such as age, genetics, biology, and environment, influence depression morbidity and mortality ( Hammen, 2018 ; Barrenetxea et al., 2022 ; Mars et al., 2022 ). Koh et al. reported that the incidence of population (70–80 years) was higher when compared with the population (60–69) ( Barrenetxea et al., 2022 ). Bai et al. also revealed that in the last 3 decades, the incidence rate of depression among older individuals has increased though the age-standard incidence rate of depression has declined in China ( Bai et al., 2022 ). In addition, the impact of other diseases such as cardiovascular diseases, obesity, and hypertension can not be ignored in recent years ( Li et al., 2022 ). Indeed, there is a bidirectional association between cardiovascular diseases ( Bobo et al., 2020 ), obesity ( Luppino et al., 2010 ), hypertension ( Jokela et al., 2014 ) and anxiety. In Korea, Park et al. found that depression increased the risk of ischemic heart disease by 38% and cerebrovascular disease by 46% among older adults through retrospective cohort study ( Park et al., 2020 ). In addition, people with cardiovascular disease have a significantly increased risk of depression ( Lesman-Leegte et al., 2009 ). An overview of a meta-analysis showed that Obese adults were 55 percent more likely to be depressed, and depressed adults were 58 percent more likely to be obese ( Luppino et al., 2010 ). Lu et al. reported that incidence of depression in China were more high in women than that in men, unemployed people than employed, and those who were separated, widowed, or divorced than people who were married or cohabiting ( Jin et al., 2021 ).

Presently, the clinical treatment strategy for depression contains first-line antidepressant drugs, cognitive-behavioral therapy, and physiotherapy ( Kverno and Mangano, 2021 ). And the first-line antidepressant drugs includes selective serotonin reuptake inhibitor (SSRIs, fluoxetine, paroxetine, and sertraline), serotonin and noradrenaline reuptake inhibitor (SNRIs, venlafaxine, and duloxetine), noradrenergic and specific serotonergic antidepressants (NaSSA, mirtazapine), serotonin receptor antagonists and reuptake inhibitors (SARIs, trazodone), monoamine oxidase inhibitor (MAOI, moclobemide), and tricyclic antidepressants (TCA, imipramine) ( Plenge et al., 2021 ). What’s more, ketamine ( Nikayin et al., 2022 ) and nitrous oxide ( Quach et al., 2022 ) are also used for the resistant depression. However, the cure rate of first-line antidepressants is low, and the adverse reactions of these drugs are obvious, and a response to conventional antidepressants requires several weeks of treatment and carries a non-negligible risk of suicide. Therefore, there is a major medical need for novel and improved antidepressant treatments. Acupuncture and herbal medicine were also used for the treatment of depression, and herbal medicine were shown to had superior efficacy and safety profiles ( Chen and Shan, 2019 ).

Scutellaria baicalensis georgi is a herbal medicine frequently used in China, and its dry root (common name: Huang-Qin in Chinese) is widely used in prescription for the treatment of depression ( Zhang et al., 2015 ; Lee et al., 2017 ). The beneficial effects of the root are due to different bioactive compounds in the brain, some of which are able to cross the blood-brain barrier (BBB). As far as it concerns scutellaria baicalensis, this corresponds to the two main flavonoids, namely, baicalin and baicalein, being purified from the plant’s dry roots ( Wang et al., 2018 ; Zhao et al., 2019 ). Previous studies have shown that scutellaria baicalensis has a wide range of pharmacological effects including anti-inflammatory, anti-oxidative, neuroprotective, antibacterial, and anti-tumor activities ( Zhao et al., 2016 ; Zhou et al., 2016 ; Zhao Yikai et al., 2018 ; Yoon et al., 2020 ). It has been found that Scutellaria baicalensis and its main components baicalin and baicalein have significant anti-depression effects and mechanism involves many aspects, such as improving the level of monoamine transmitter brain neurotrophic factor, regulating the HPA axis, anti-inflammation, anti-oxidation and promoting neurogenesis ( Hai-Yang et al., 2016 ; Pazini Francis et al., 2017 ). In addition, as a traditional medicine, Scutellaria baicalensis has produced neuroprotective effects in various models of Parkinson’s disease ( Mu X. et al., 2011 ), Alzheimer’s disease ( Zhao J. et al., 2018 )and so on. Recent studies have shown that baicalin and baicalein, in addition to protecting dopaminergic neurons from mitochondrial and oxidation-related toxicity, may also have a beneficial effect on DA-related brain diseases by increasing DA levels in the brain ( Im H. I. et al., 2005 ; Zhao J. et al., 2018 ).

At present, accumulating evidence from the pharmacological effect indicated that scutellaria baicalensis may have great potential in treating depression. Nevertheless, up to now, the pre-clinical studies on scutellaria baicalensis for depression have not been systematically evaluated and summarized. In this study, we conducted a rigorous and comprehensive systematic review and meta-analysis of recent literature on the treatment of depression model animals by scutellaria baicalensis, and explored different behavioral changes and potential mechanisms, aiming to provide evidence and guidance for clinical practice.

2 Materials and methods

2.1 search strategies.

We searched relevant databases, including PubMed, Web of Science, Embase, and CNKI from inception to September 2023. The main search terms were composed by “Scutellaria baicalensis” or Radix Scutellariae [tiab] OR Scutellaria [tiab] OR baicalin [Mesh] OR baicalein [Mesh] AND (Depression [Mesh] OR “Depressive disorder” [Mesh] OR Depress [tiab] OR “emotional disorder” [tiab] OR “psychological disorder” [tiab] OR “psychological distress” [tiab] OR “emotional distress” [tiab] OR “emotional stress" [tiab]. Subsequently, the two researchers (Ying Ma and Xun Zhou) independently reviewed the title/abstract related to the topic. A full-text read was also performed to find the potential documents that met the eligibility criteria. Importantly, any disagreements between the two researchers were resolved through negotiation or thirdparty consensus.

2.2 Inclusion and exclusion criteria

Studies were be included when they meet the following criteria: (1) in vivo studies on animal subjects; (2) the animal disease model was depressive disorder model; (3) animals were treated with scutellaria baicalensis or its active components baicalin and baicalin; (4) the data included in the literature were represented by mean and standard (SD) or can be converted to mean and SD. Exclusion criteria are as follows: (1) other types of studies ( in vitro studies, case reports, clinical trials, reviews, abstracts or comments), (2) combination with other compounds, (3) not depressive disorder model, (5) studies with insufficient data, (6) the sample size of control group and scutellaria treatment group was less than three animals. (7) plagiarism or duplicate publication of literature.

2.3 Data extraction

General data, intervention measures, efficacy indicators, test results and other data of patients were independently extracted by two researchers (Ying Ma and Xun Zhou) according to a unified table and cross-checked. The following information for each study include: (1) the year of publication of the first author’s name; (2) characteristics of the animal, including species, number, sex, weight, etc.; (3) the establishment of depression model and anesthesia used in the model; (4) Characteristics of intervention, including dose and route of administration; (5) main outcome indicators and differences between groups. If the main data were lost or displayed in a graphical manner, we would contact the publishers to obtain the original data. The values in the graph were measured by digital ruler software without receiving any reply from the author.

2.4 Quality assessment of included studies

The methodological quality of the included studies was evaluated by independently two investigators (Ying Ma and Xun Zhou) according to the Collaborative Approach to Meta-Analysis and Review of Animal Data from Experimental Studies (CAMARADES)’s risk of bias tool ( Macleod et al., 2004 ). The terms for quality assessment included 1) peer reviewed publication; 2) control of temperature; 3) random allocation to groups; 4) blinded induction of depression; 5) blinded assessment of behavioral outcome; 6) use of anesthetic without significant intrinsic neuroprotective activity; 7) calculation of the sample size necessary to achieve sufficient power; 8) appropriate animal model which uses animals without relevant comorbidities (aged, diabetic, or hypertensive); 9) compliance with animal welfare Regulations; 10) statement of potential conflict of interests. Any disagreements between the two researchers were resolved through negotiation or third party consensus.

2.5 Statistical analysis

Meta-analysis was performed using Review Manager (RevMan v5.3) software. Outcome measures were all expressed as continuous data and standardized mean difference (SMD) with 95% confidence interval (CI). If there was no statistical heterogeneity among studies ( p ≥ 0.10, I 2 ≤ 5%), fixed-effect model was used for analysis. Otherwise, random effect model is used to analyze. Probability value p < 0.05 was considered statistically significant.

3.1 Study selection

In the initial search of databases, 373 literature were retrieved. After eliminating redundant and irrelevant articles, 84 records remained. Subsequently, the investigators screened the titles and abstracts, and 26 studies were exclude. After reviewing the full-text articles carefully, 10 studies were excluded for at least one of the following reasons: (1) metabolites were studied; (2) no relevant outcome; (3) review article. Ultimately, 13 studies were included in this meta analysis. The search strategy built on this study using the PRISMA method ( Moher et al., 2009 ) is described in Figure 1 .

www.frontiersin.org

Figure 1 . Summary of the process for identifying candidate studies.

3.2 Characteristics of included studies

The basic characteristics of the 13 studies were shown in Table 1 . The meta-analysis included 270 animals (136 in the model group and 134 in the Scutellaria baicalensis treatment group) in 13 studies.

www.frontiersin.org

Table 1 . Characteristics of studies included in systematic review of antidepressant effects of Scutellaria baicalensis.

3.2.1 Animals

C57BL/6 mice were used in 4 studies ( Zhang et al., 2016 ; Zhang Kuo et al., 2019 ; Fan et al., 2020 ; Zhao et al., 2021 ), ICR mice were used in 3 studies ( Zhang Ruyi et al., 2019 ; Li-Ting et al., 2019 ; Jia et al., 2021 ), and non-obese diabetic mice was used in only one study; Sprague Dawley rats were used in 4 studies ( Xiong et al., 2011 ; Lee et al., 2013 ; Zhang et al., 2018 ; Zhang Kuo et al., 2019 ), and Wistar rats was used in one study ( Liu et al., 2019 ). All but one of the studies involved males ( Fan et al., 2020 ); The body weight of Sprague Dawley rats ranged from 160 g to 280 g, while the body weight of mice ranged from 18 g to 26 g. In the studies included in this meta-analysis, Chronic unpredictability mild stress (CUMS), corticosterone (CORT), rotenone, experimental autoimmune prostatitis (EAP), olfactory bulbectomy (OBX), and repeated restraint stress were used to construct the animal depression model. Currently, it is defined that chronic unpredictability mild stress (CUMS) is a valuable model to evaluate the etiology of depression. Among these studies, CUMS was adopted in six studies ( Xiong et al., 2011 ; Zhang et al., 2016 ; Zhang et al., 2018 ; Zhang Ruyi et al., 2019 ; Liu et al., 2019 ; Jia et al., 2021 ). Long-term exposure to CORT was used in three studies ( Zhang Kuo et al., 2019 ; Li-Ting et al., 2019 ; Fan et al., 2020 ). Rotenone ( Zhao et al., 2021 ), EAP ( Zhong et al., 2019 ), OBX ( Zhang Kuo et al., 2019 ), and repeated restraint stress ( Lee et al., 2013 ) were also applied in one studies, respectively.

3.2.2 Interventions

The animals in eight studies were treated with baicalin ( Zhang et al., 2016 ; Zhang Kuo et al., 2019 ; Zhang Ruyi et al., 2019 ; Li-Ting et al., 2019 ; Liu et al., 2019 ; Fan et al., 2020 ; Jia et al., 2021 ), four with baicalein ( Xiong et al., 2011 ; Lee et al., 2013 ; Zhong et al., 2019 ; Zhao et al., 2021 ), and one with Radix Scutellariae ( Zhang et al., 2018 ). In the 13 studies, the duration of drug administration varied, with five studies lasting 3 weeks ( Xiong et al., 2011 ; Zhang et al., 2018 ; Zhang Ruyi et al., 2019 ; Li-Ting et al., 2019 ; Jia et al., 2021 ), two studies lasting 4 weeks ( Zhang Kuo et al., 2019 ; Zhao et al., 2021 ), two studies lasting 6 weeks ( Zhang et al., 2016 ; Fan et al., 2020 ), two study lasting 2 weeks ( Lee et al., 2013 ; Zhang Kuo et al., 2019 ), one study lasting 1 weeks ( Zhong et al., 2019 ), and one study lasting 5 weeks ( Zhang et al., 2016 ). All drugs were administered intragastrically and vehicles or saline were administered to the control group in all studies.

3.3 Methodological quality

The assessment of the quality of these studies included in these work was conducted from CAMARADES. As shown in table 2 , the quality score ranged from 6 to 7, with median of 6.615. All of the studies have been peer-reviewed and reported. All studies have reported that animals were randomly divided into groups and blinded assessment of behavioral outcome. In addition, there were no study reported blinded induction of depression.

www.frontiersin.org

Table 2 . Quality assessment of studies included in systematic review of antidepressant effects of Scutellaria Baicalensis following modified scale of CAMARADES.

3.4 Effects of scutellaria baicalensis on depression

3.4.1 outcome measures.

The outcome measures in the 13 studies included behavioral change, physiological change, and histological analysis. For the measurment of behavioral change, six behavioral tests were commonly used, namely, sucrose preference test (SPT) ( Zhang et al., 2016 ; Zhang et al., 2018 ; Zhang Ruyi et al., 2019 ; Li-Ting et al., 2019 ; Liu et al., 2019 ; Fan et al., 2020 ; Jia et al., 2021 ; Zhao et al., 2021 ), open field test (OFT) ( Xiong et al., 2011 ; Lee et al., 2013 ; Zhang et al., 2016 ; Zhang et al., 2018 ; Zhang Ruyi et al., 2019 ; Zhong et al., 2019 ; Fan et al., 2020 ; Jia et al., 2021 ; Zhao et al., 2021 ), morris water maze test ( Zhang et al., 2018 ; Jia et al., 2021 ), tail suspension test ( Zhang et al., 2016 ; Zhang Kuo et al., 2019 ; Zhang Ruyi et al., 2019 ; Zhong et al., 2019 ; Fan et al., 2020 ; Jia et al., 2021 ; Zhao et al., 2021 ), novelty suppressed feeding test (NSFT) ( Fan et al., 2020 ; Jia et al., 2021 ), forced swimming test ( Xiong et al., 2011 ; Lee et al., 2013 ; Zhang et al., 2016 ; Zhang Kuo et al., 2019 ; Li-Ting et al., 2019 ; Zhong et al., 2019 ; Fan et al., 2020 ). For the determination of physiological change, body weight, sucrose intake and sleep were assessed ( Liu et al., 2019 ; Jia et al., 2021 ). For the detection of histological analysis, all of the studies have all focused on the hippocampus, and some of these studies also assessed a broader range of regions, such as striatum ( Zhao et al., 2021 ), paraventrnucleus ( Lee et al., 2013 ), cortex ( Lee et al., 2013 ; Liu et al., 2019 ; Zhao et al., 2021 ), midbrain ( Zhao et al., 2021 ) or brain stem ( Zhao et al., 2021 ).

3.4.2 Effects of scutellaria baicalensis on depression by SPT analysis

A total of eight studies ( Zhang et al., 2016 ; Zhang et al., 2018 ; Zhang Ruyi et al., 2019 ; Li-Ting et al., 2019 ; Liu et al., 2019 ; Fan et al., 2020 ; Jia et al., 2021 ; Zhao et al., 2021 )compared the differences in SPT before and after treatment with 158 animals, including 78 in the experimental group and 80 in the control group. Due to significant heterogeneity between studies ( p < 0.00001, I 2 = 90%), the random-effects model was adopted. The difference between the two groups was statistically significant [SMD = −2.80, 95%CI(-4.03, -1.57), p < 0.01], suggesting that scutellaria baicalensis could significantly enhance the sucrose preference rate in depressed animals, as shown in Figure 2A .

www.frontiersin.org

Figure 2 . Forest plot of studies investigating the effect of Scutellaria baicalensis on animal behavior. The protective effects of Scutellaria baicalensis on animal behavior by (A) SPT, (B) TST, (C) OFT, (D) NSFT, (E) MWM, and (F) FST analysis.

3.4.3 Effects of scutellaria baicalensis on depression by TST analysis

The analysis of TST was applied in seven studies ( Zhang et al., 2016 ; Zhang Kuo et al., 2019 ; Zhang Ruyi et al., 2019 ; Zhong et al., 2019 ; Fan et al., 2020 ; Jia et al., 2021 ; Zhao et al., 2021 ) that had a total sample size of 148, of which 73 animals received Scutellaria baicalensis and 75 received a vehicle or saline treatment, while the analysis of FST covered eight studies ( Xiong et al., 2011 ; Lee et al., 2013 ; Zhang et al., 2016 ; Zhang Kuo et al., 2019 ; Li-Ting et al., 2019 ; Zhong et al., 2019 ; Fan et al., 2020 )with 168 animals, 84 in the experimental group and 84 in the control group. There were significant heterogeneity among the studies ( p < 0.00001, I 2 = 92%; p < 0.00001, I 2 = 85%), the random-effect model was adopted. Results as shown in Figures 2B, F , immobility time was dramatically reduced in the Scutellaria baicalensis group versus control group, the difference was no statistically significant ([SMD = 1.89, 95%CI(0.29, 3.49), p = 0.02]; [SMD = 0.34, 95%CI(-0.57, 1.24), p = 0.47].)

3.4.4 Effects of scutellaria baicalensis on depression by OFT analysis

In OFT, meta-analysis of nine studies ( Xiong et al., 2011 ; Lee et al., 2013 ; Zhang et al., 2016 ; Zhang et al., 2018 ; Zhang Ruyi et al., 2019 ; Zhong et al., 2019 ; Fan et al., 2020 ; Jia et al., 2021 ; Zhao et al., 2021 )had a total sample size of 170, of which 84 animals received Scutellaria baicalensis and 86 received a vehicle or saline treatment. There was Statistically significant between groups in the number of crossings and rearing, indicating that Scutellaria baicalensis treatment can ameliorate the frequency of crossing and rearing compared with the control group [SMD = −2.38, 95%CI(-3.53, -1.23), p < 0.01], as shown in Figure 2C .

3.4.5 Effects of scutellaria baicalensis on depression by NFST analysis

In the NSFT experiment ( Fan et al., 2020 ; Jia et al., 2021 ), food consumption was increased [SMD = −2.98, 95%CI(-3.94, -2.02), p < 0.01 in Scutellaria baicalensis group compared to control group. In contrast, there was no statistically significant differences in the MWM ( Zhang et al., 2018 ; Jia et al., 2021 ), implying that Scutellaria baicalensis administration did not affect the times of platform crossings and seconds spent in the target quarter [SMD = −0.83, 95%CI(-2.38,0.72), p = 0.29; Figure 2E ].

3.5 Underlying mechanisms

Most of the included literature is based on studies of the neuroprotective effects of Scutellaria baicalensis on depression. Brain-derived neutrophic factor (BDNF) ( Xiong et al., 2011 ; Lee et al., 2013 ; Zhang et al., 2018 ; Li-Ting et al., 2019 ; Jia et al., 2021 ; Zhao et al., 2021 ), extracellular-signal-regulated kinase (ERK) phosphorylation ( Xiong et al., 2011 ; Zhang et al., 2016 ; Jia et al., 2021 ), cAMP response element-binding protein (CREB) phosphorylation ( Zhang et al., 2018 ; Jia et al., 2021 ; Zhao et al., 2021 ), tropomyosin-related kinase B (TrkB) phosphorylation ( Zhao et al., 2021 ), protein kinase A (PKA) phosphorylation ( Zhang et al., 2018 ), phosphatidylinositol 3-kinasep (PI3K) phosphorylation ( Fan et al., 2020 ), Glycogen synthase kinase-3 beta (GSK3b)phosphorylation ( Fan et al., 2020 ), Protein Kinase B (AKT) phosphorylation ( Zhang Kuo et al., 2019 ; Fan et al., 2020 ), NF-kB p65 phosphorylation ( Zhong et al., 2019 ), inhibitor of kB (IkB) phosphorylation ( Zhong et al., 2019 ), Fibroblast growth factor (FGF) ( Zhang Ruyi et al., 2019 ), Forkhead box G1 (FOXG1) ( Zhang Ruyi et al., 2019 ), Serum/Glucocorticoid Regulated Kinase 1(SGK-1) ( Li-Ting et al., 2019 ), N-methyl-D-aspartate receptor 2B (NR2B) ( Zhang et al., 2016 ), and CaMKII ( Zhang et al., 2016 ) were studied. Mechanistically, by acting as partial, subtype-selective GABAA receptor ligands, scutellaria baicalensis and its bioactive ingredients (baicalin and baicalein) foster the interaction of GABAA receptors with TrkB to potentiate GABA-induced signaling. By increasing cAMP/pERK and PI3K/pAKT signaling, they promote the synthesis of neurotrophic factors (BDNF and NGF) as well as neurogenesis.

As far as monoamine neurotransmitters is concerned, dopamine (DA) ( Lee et al., 2013 ; Zhao et al., 2021 ), 3,4-dihydroxyphenylacetic acid (DOPAC) ( Lee et al., 2013 ; Zhao et al., 2021 ), homovanillic acid (HVA) ( Lee et al., 2013 ; Zhao et al., 2021 ) serotonin (5-HT) ( Lee et al., 2013 ; Zhao et al., 2021 ), 5-hydroxyindole-acetic acid (5-HIAA) ( Zhao et al., 2021 ), and noradrenaline (NE) ( Zhao et al., 2021 ) were assessed. In addition, serum Corticosterone ( Zhang Kuo et al., 2019 ; Li-Ting et al., 2019 ; Liu et al., 2019 ), glucocorticoid receptor phosphorylation in hypothalamus ( Zhang Kuo et al., 2019 ; Li-Ting et al., 2019 ), corticotrophin-releasing factor (CRF)in hypo-thalamic ( Lee et al., 2013 ), and tyrosine hydroxylase (TH)in hypo-thalamic ( Lee et al., 2013 ) were evaluated. BrdU + ( Zhang et al., 2018 ; Zhang Ruyi et al., 2019 ; Fan et al., 2020 ), NeuN + ( Zhang et al., 2018 ; Zhang Ruyi et al., 2019 ; Fan et al., 2020 ) and DCX + ( Zhang et al., 2018 ; Fan et al., 2020 ) in DG; SLC6A4 [473], IDO ( Zhong et al., 2019 ) GFAP (for astrocytes) ( Zhong et al., 2019 ), Iba1 (for microglia) ( Zhong et al., 2019 ) in the CA1, CA3, andDG ( Zhong et al., 2019 ); taurine (Tau)/totalcreatine (tCr,creatine + phosphocreatine), glutamate + glutamine (Glx)/tCr in the hippocampus ( Zhong et al., 2019 ); and TUNEL-positive cells in the hippocampus ( Zhang Kuo et al., 2019 ) were also examined. Additionally, α-synuclein ( Zhao et al., 2021 ), PSD95 ( Fan et al., 2020 ; Zhao et al., 2021 ), and SYP ( Zhang Kuo et al., 2019 ; Fan et al., 2020 ; Zhao et al., 2021 ) were also studied. Actually, By acting as MAO A/B inhibitors, scutellaria baicalensis induce monoamine, and mostly DA release.

To determine the anti-inflammatory effects of Scutellaria baicalensis during depression, IFN-γ, TNF-α, IL-1β, IL-2, IL-4, IL-5, IL-6, IL-10, IL-12 in plasma ( Zhao et al., 2021 ) and TNF-α, IL-1β, IL-6, IL-8, IL-18 in the hippocampus ( Zhong et al., 2019 ) were studied respectively. Furthermore, inflammatory factors such as IL-1β, IL-6, and TNF-α were measured both in the serum and in the hippocampus ( Zhang et al., 2016 ). In terms of chronic oxidative stress and apoptosis, COX-2 in the frontal cortex and hippocampus ( Liu et al., 2019 ), PGE 2 in the frontalcortex and hippocampus ( Liu et al., 2019 ), SOD ( Zhang Kuo et al., 2019 ), MDA ( Zhang Kuo et al., 2019 ), GSH ( Zhang Kuo et al., 2019 ), Apaf-1 caspase-3 ( Zhang Kuo et al., 2019 ), caspase-9 ( Zhang Kuo et al., 2019 )in the hippocampus, [Ca 2+ ] ( Zhang et al., 2016 ) and ROS ( Zhang et al., 2016 ) were mainly appraised.

4 Discussion

Depression is a common mental disease associated with high morbidity and huge social burden. Numerous preclinical studies have shown that Scutellaria baicalensis and its active constituents are effective for depression. The aim of this study is to systematically review the roles of scutellaria baicalensis in depression and summarize the possible mechanism. To our knowledge, it is a first systematic review and meta-analysis of preclinical studies on the efficacy of Scutellaria baicalensis and its main components in animal depression model. The results indicated that Scutellaria baicalensis can remarkably safeguard against depression evidenced by improved behavioral changes. And this activities were associated with the regulation of Scutellaria baicalensis on inflammatory responses, oxidative stress, apoptosis, and neurotransmitters production via modulating TrkB-BDNF, PI3K-AKT, MAPK and NF-κB pathways.

In this work, 13 studies were included to assess the efficacy of scutellaria baicalensis on depression. Chronic unpredictability mild stress, corticosterone, rotenone-induced depression model, experimental autoimmune prostatitis (EAP)-induced depression mice model, olfactory bulbectomy (OBX) depression mice model and repeated restraint stress-induced depression rat model were used to study the antidepressant effect of Scutellaria baicalensis, while sucrose preference test (SPT), open field test (OFT), Morris water maze test (MWM), tail suspension test (TST), novelty suppressed feeding test (NSFT), and forced swimming test (FST) were adopted to evaluate the efficacy.

So far, the anti-depressive actvities of scutellaria baicalensis are welly studied, and the commonly used animal models are CUMS ( Xiong et al., 2011 ; Zhang et al., 2016 ; Zhang et al., 2018 ; Zhang Ruyi et al., 2019 ; Liu et al., 2019 ; Jia et al., 2021 )and CORT ( Zhang Kuo et al., 2019 ; Li-Ting et al., 2019 ; Fan et al., 2020 ), etc., and one of the criteria to evaluate the success of depression model and the efficacy of anti-depression is behavioral test. Sucrose preference test for evaluating degree of pleasure lack of mice, open field test reflect the spontaneous activity in mice and explore the behavior, forced swimming test and tail suspension test reflects the behavior of the mice desperation, reaction ability of learning and memory in mice water maze experiment, while novelty suppressed feeding test, the variation of the lack of animal euphoria ( Lu et al., 2016 ). In a mouse model of chronic cort-induced depression, baicalin significantly ameliorates behavior change by reducing the time spent in the central area of the open field test and the time spent in the cross maze test with open arms, and increasing the immobile time in the tail suspension test and forced swimming test. ( Zhang et al., 2016 ; Zhang Kuo et al., 2019 ). On the other hand, Scutellaria baicalensis alleviated depression-like behavior by increasing sucrose consumption and reducing the immobile time of tail suspension and forced swimming tests in mild stress chronic mouse model (CUMS) ( Li-Ting et al., 2019 ; Liu et al., 2019 ; Zhong et al., 2019 ).

The anti-depressive mechanism of scutellaria baicalensis is still not fully understand. Scutellaria baicalensis and its active components have a wide range of antidepressive effects. This review shows that most studies have focused on neural protection by measuring BDNF, ERK, CREB, TrkB, PI3K, GSK3B, AKT, NF-KB P65, IkB and their phosphorylation ( Xiong et al., 2011 ; Lee et al., 2013 ; Zhang et al., 2018 ; Zhang Kuo et al., 2019 ; Li-Ting et al., 2019 ; Zhong et al., 2019 ; Fan et al., 2020 ; Jia et al., 2021 ; Zhao et al., 2021 ). Neuroinflammation was concerned by detecting inflammatory cytokines IL-1β, IL-6 and TNF-α in serum and/or hippocampus ( Zhang et al., 2016 ; Zhong et al., 2019 ; Zhao et al., 2021 ). Monoamine neurotransmitters including dopamine, 3, 4-dihydroxyphenylacetic acid, hypervanilic acid, serotonin (5-HT), 5-hydroxyindoleacetic acid, and norepinephrine were evaluated ( Lee et al., 2013 ; Zhao et al., 2021 ). Oxidative stress and apoptosis were studied by measuring COX-2,SOD, MDA, GSH, APAF1 Caspase-3, Caspase-9, [Ca 2+ ]and ROS levels in frontal lobe and hippocampus ( Zhang et al., 2016 ; Zhang Kuo et al., 2019 ; Liu et al., 2019 ). Moreover, protein expressions of the presynaptic marker (synaptophysin1) and the postsynaptic marker (PSD95) and so on were studied following baicalin treatment ( Fan et al., 2020 ; Zhao et al., 2021 ). The included studies mostly confirmed that scutellaria baicalensis regulated monoamine neurotransmitter levels and inflammatory factors. In addition, scutellaria baicalensis and its active components can also regulate oxidative stress, apoptosis, and synaptic dysfunction.

These results resembled theoretical study. Studies have reported that scutellaria baicalensis may induce the release of monoamine (DA) and enhance GABA-induced signal transduction, thereby increasing cAMP/pERK and PI3K/pAKT signals, and promoting the synthesis and neurogenesis of neurotrophic factors (BDNF and NGF) ( Im Heh-In et al., 2005 ; Mu Xin et al., 2011 ). Secondly, scutellaria baicalensis plays an anti-inflammatory role by decreasing the levels of inducible nitric oxide synthase, NF-κB and pro-inflammatory cytokines TNF-α, IL-6 and IL-1β ( Ma et al., 2015 ). It is reported that scutellaria baicalensis can also improve mitochondrial membrane potential depolarization and ATP production, and increase AMPK to enhance mitochondrial autophagy and mitochondrial biogenesis, thus playing a protective role in mitochondria ( Zhang et al., 2017 ). It also lowers levels of reactive oxygen species and nitrogen species, increases superoxide dismutase, glutathione, glutathione peroxidase and catalase activities, heat shock protein 70, heme oxygenase-1 and thioredoxin levels, and ultimately reduces lipid peroxidation. The content of malondialdehyde and lipoxygenase are decreased by Scutellaria baicalensis. It also inhibited p-P38, Bax/Bcl-2 ratio, caspase 3, caspase 6, caspase 9, and cytochrome C release, thereby inhibiting apoptosis ( Liu et al., 2012 ; Wang et al., 2013 ; Li et al., 2019 ).

This study was screened strictly in accordance with the inclusion criteria, exclusion criteria and literature quality scoring criteria, but there may still be the following limitations that may affect the accuracy of the study: First, the databases searched in this review were all in English, so there may be some deviations; Second, the methodological quality of the included studies was moderate, with none of the studies reporting the blinded induction of depression and the sample size needed to calculate it to obtain sufficient power; Third, the lack of negative studies may lead to overestimation of the true role of Scutellaria baicalensis. Fourthly, in the included studies, there were significant differences in depression modeling method and time, dosage and treatment time of scutellaria baicalensis.

5 Conclusion

In this preclinical systematic review, scutellaria baicalum can improve the symptoms of anhedonia, reduce the degree of behavioral despair, improve the cognitive ability of mice and play an anti-depressive effect in experimental depression. The mechanism mainly includes antioxidant, anti-inflammatory, neurotransmitter regulation, and inhibition of apoptosis. Therefore, scutellaria baicalensis may be a candidate for further clinical trials of depression.

Data availability statement

The original contributions presented in the study are included in the article/ Supplementary material , further inquiries can be directed to the corresponding authors.

Author contributions

YM: Data curation, Formal Analysis, Writing–original draft. XZ: Visualization, Writing–review and editing. FZ: Funding acquisition, Writing–review and editing. CH: Formal Analysis, Writing–review and editing. HY: Software, Writing–review and editing. WC: Writing–original draft. XT: Writing–review and editing.

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This research was funded by National Natural Science Foundation of China (Grant 81830109).

Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher’s note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

Supplementary material

The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fphar.2024.1313871/full#supplementary-material

Bai, R., Dong, W., Peng, Q., and Bai, Z. (2022). Trends in depression incidence in China, 1990-2019. J. Affect Disord. 296, 291–297. doi:10.1016/j.jad.2021.09.084

PubMed Abstract | CrossRef Full Text | Google Scholar

Barrenetxea, J., Pan, A., Feng, Q., and Koh, W. P. (2022). Factors associated with depression across age groups of older adults: the Singapore Chinese health study. Int. J. Geriatr. Psychiatry 37. undefined. doi:10.1002/gps.5666

CrossRef Full Text | Google Scholar

Bobo, W. V., Ryu, E., Petterson, T. M., Lackore, K., Cheng, Y., Liu, H., et al. (2020). Bi-directional association between depression and HF: an electronic health records-based cohort study. J. Comorb 10, 2235042X20984059. doi:10.1177/2235042X20984059

Chen, C., and Shan, W. (2019). Pharmacological and non-pharmacological treatments for major depressive disorder in adults: a systematic review and network meta-analysis. Psychiatry Res. 281, 112595. doi:10.1016/j.psychres.2019.112595

Dwyer Jennifer, B., Awais, A., Rajiv, R., Widge, A., Rodriguez, C. I., Carpenter, L. L., et al. (2020). Hormonal treatments for major depressive disorder: state of the art. Am. J. Psychiatry 177, 686–705. doi:10.1176/appi.ajp.2020.19080848

Fan, Z., Tao, W., Shang, Z., Zhang, W., Ruan, J., Zhang, C., et al. (2020). Facilitating granule cell survival and maturation in dentate gyrus with baicalin for antidepressant therapeutics. Front. Pharmacol. 11, 556845. doi:10.3389/fphar.2020.556845

Hai-Yang, Y., Yin, Z.-J., Yang, S.-J., Ma, S. P., and Qu, R. (2016). Baicalin reverses depressive-like behaviours and regulates apoptotic signalling induced by olfactory bulbectomy. Phytotherapy Res. PTR 30 (3), 469–475. doi:10.1002/ptr.5550

Hammen, C. (2018). Risk factors for depression: an autobiographical review. Annu. Rev. Clin. Psychol. 14, 1–28. doi:10.1146/annurev-clinpsy-050817-084811

Im, H. I., Joo, W. S., Nam, E., Lee, E. S., Hwang, Y. J., and Kim, Y. S. (2005). Baicalein prevents 6-hydroxydopamine-induced dopaminergic dysfunction and lipid peroxidation in mice. Pharmacol 98, 185–189. doi:10.1254/jphs.sc0050014

Im, H.-I., Wan Seok, J., Nam, E., Lee, E. S., Hwang, Y. J., and Kim, Y. S. (2005). Baicalein prevents 6-hydroxydopamine-induced dopaminergic dysfunction and lipid peroxidation in mice. J. Pharmacol. Sci. 98, 185–189. doi:10.1254/jphs.sc0050014

Jain, S., Gupta, S., Li, V. W., Suthoff, E., and Arnaud, A. (2022). Humanistic and economic burden associated with depression in the United States: a cross-sectional survey analysis. BMC Psychiatry 22 (1), 542. doi:10.1186/s12888-022-04165-x

Jia, Z., Yang, J., Cao, Z., Zhao, J., Zhang, J., Lu, Y., et al. (2021). Baicalin ameliorates chronic unpredictable mild stress-induced depression through the BDNF/ERK/CREB signaling pathway. Behav. Brain Res. 414, 113463. undefined. doi:10.1016/j.bbr.2021.113463

Jin, L., Xu, X., Huang, Y., Li, T., Ma, C., Xu, G., et al. (2021). Prevalence of depressive disorders and treatment in China: a cross-sectional epidemiological study. Lancet Psychiatry 8, 981–990. doi:10.1016/S2215-0366(21)00251-0

Jokela, M., Hamer, M., Singh-Manoux, A., Batty, G. D., and Kivimäki, M. (2014). Association of metabolically healthy obesity with depressive symptoms: pooled analysis of eight studies. Mol. Psychiatry 19 (8), 910–914. doi:10.1038/mp.2013.162

Kessler Ronald, C., and Bromet Evelyn, J. (2013). The epidemiology of depression across cultures. Annu. Rev. Public Health 34, 119–138. doi:10.1146/annurev-publhealth-031912-114409

Kverno, K. S., and Mangano, E. (2021). Treatment-resistant depression: approaches to treatment. J. Psychosoc. Nurs. Ment. Health Serv. 59 (9), 7–11. doi:10.3928/02793695-20210816-01

Lee, B., Sur, B., Park, J., Kim, S. H., Kwon, S., Yeom, M., et al. (2013). Chronic administration of baicalein decreases depression-like behavior induced by repeated restraint stress in rats. Korean J. Physiol. Pharmacol. 17, 393–403. doi:10.4196/kjpp.2013.17.5.393

Lee, H. W., Ryu, H. W., Kang, M. G., Park, D., Lee, H., Shin, H. M., et al. (2017). Potent inhibition of monoamine oxidase A by decursin from Angelica gigas Nakai and by wogonin from Scutellaria baicalensis Georgi. Int. J. Biol. Macromol. 97, 598–605. doi:10.1016/j.ijbiomac.2017.01.080

Lesman-Leegte, I., van Veldhuisen, D. J., Hillege, H. L., Moser, D., Sanderman, R., and Jaarsma, T. (2009). Depressive symptoms and outcomes in patients with heart failure: data from the COACH study. Eur. J. Heart Fail 11 (12), 1202–1207. doi:10.1093/eurjhf/hfp155

Li, G. H., Cheung, C. L., Chung, A. K., Cheung, B. M. Y., Wong, I. C. K., Fok, M. L. Y., et al. (2022). Evaluation of bi-directional causal association between depression and cardiovascular diseases: a Mendelian randomization study. Psychol. Med. 52 (9), 1765–1776. doi:10.1017/S0033291720003566

Li, Q., Li, Q. Q., Jia, J. N., Sun, Q. Y., Zhou, H. H., Jin, W. L., et al. (2019). Baicalein exerts neuroprotective effects in FeCl3-induced posttraumatic epileptic seizures via suppressing ferroptosis. Front. Pharmacol. 10, 638. doi:10.3389/fphar.2019.00638

Li-Ting, G., Wang, S.-Q., Su, J., Xu, L. X., Ji, Z. Y., Zhang, R. Y., et al. (2019). Baicalin ameliorates neuroinflammation-induced depressive-like behavior through inhibition of toll-like receptor 4 expression via the PI3K/AKT/FoxO1 pathway. J. Neuroinflammation 16, 95. doi:10.1186/s12974-019-1474-8

Liu, L., Dong, Y., Xin, S., Xia, B., and Wang, H. (2019). Anti-depressive effectiveness of baicalin in vitro and in vivo . Molecules 24, 326. undefined. doi:10.3390/molecules24020326

Liu, Y.-F., Gao, F., Xiao-Wei, L., Jia, R. H., Meng, X. D., Zhao, R., et al. (2012). The anticonvulsant and neuroprotective effects of baicalin on pilocarpine-induced epileptic model in rats. Neurochem. Res. 37, 1670–1680. doi:10.1007/s11064-012-0771-8

Lu, Y., Hu, Q., Mak Marvin, S. H., Lou, J., Xu, S. L., Bi, C. W. C., et al. (2016). A Chinese herbal decoction, reformulated from Kai-Xin-San, relieves the depression-like symptoms in stressed rats and induces neurogenesis in cultured neurons. Sci. Rep. 6, 30014. doi:10.1038/srep30014

Luppino, F. S., de Wit, L. M., Bouvy, P. F., Stijnen, T., Cuijpers, P., Penninx, B. W. J. H., et al. (2010). Overweight, obesity, and depression: a systematic review and meta-analysis of longitudinal studies. Arch. Gen. Psychiatry 67 (3), 220–229. doi:10.1001/archgenpsychiatry.2010.2

Ma, P., Mao, X. Y., Li, X. L., Ma, Y., Qiao, Y. D., Liu, Z. Q., et al. (2015). Baicalin alleviates diabetes-associated cognitive deficits via modulation of mitogen-activated protein kinase signaling, brain-derived neurotrophic factor and apoptosis. Mol. Med. Rep. 12, 6377–6383. doi:10.3892/mmr.2015.4219

Macleod, M. R., O’Collins, T., Howells, D. W., and Donnan, G. A. (2004). Pooling of animal experimental data reveals influence of study design and publication bias. Stroke 35, 1203–1208. doi:10.1161/01.STR.0000125719.25853.20

Mars, N., Kerminen, S., Feng, Y. A., Kanai, M., Läll, K., Thomas, L. F., et al. (2022). Genome-wide risk prediction of common diseases across ancestries in one million people. Cell Genom 2 (4), 100118. None. doi:10.1016/j.xgen.2022.100118

Moher, D., Liberati, A., Tetzlaff, J., and Altman, D. G.PRISMA Group (2009). Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement. Clin. Epidemiol. 62, 1006–1012. doi:10.1016/j.jclinepi.2009.06.005

Mu, X., Guo-Rong, H., Yuan, X., Li, X. X., and Du, G. H. (2011b). Baicalein protects the brain against neuron impairments induced by MPTP in C57BL/6 mice. Pharmacol. Biochem. Behav. 98, 286–291. doi:10.1016/j.pbb.2011.01.011

Mu, X., He, G. R., Yuan, X., Li, X. X., and Du, G. H. (2011). Baicalein protects the brain against neuron impairments induced by MPTP in C57BL/6 mice. Pharmacol. Biochem. Behav. 98, 286–291. doi:10.1016/j.pbb.2011.01.011

Nikayin, S., Murphy, E., Krystal, J. H., and Wilkinson, S. T. (2022). Long-term safety of ketamine and esketamine in treatment of depression. Expert Opin. Drug Saf. 21 (6), 777–787. doi:10.1080/14740338.2022.2066651

Park, D. H., Cho, J. J., Yoon, J. L., Kim, M. Y., and Ju, Y. S. (2020). The impact of depression on cardiovascular disease: a nationwide population-based cohort study in Korean elderly. Korean J. Fam. Med. 41 (5), 299–305. doi:10.4082/kjfm.18.0134

Pazini Francis, L., Cunha Mauricio, P., Azevedo, D., Rosa, J. M., Colla, A., de Oliveira, J., et al. (2017). Creatine prevents corticosterone-induced reduction in hippocampal proliferation and differentiation: possible implication for its antidepressant effect. Mol. Neurobiol. 54 (8), 6245–6260. doi:10.1007/s12035-016-0148-0

Plenge, P., Yang, D., Salomon, K., Laursen, L., Kalenderoglou, I. E., Newman, A. H., et al. (2021). The antidepressant drug vilazodone is an allosteric inhibitor of the serotonin transporter. Nat. Commun. 12 (1), 5063. doi:10.1038/s41467-021-25363-3

Quach, D. F., de Leon, V. C., and Conway, C. R. (2022). Nitrous Oxide: an emerging novel treatment for treatment-resistant depression. J. Neurol. Sci. 434, 120092. doi:10.1016/j.jns.2021.120092

Vos, T., Abajobir, A. A., Abate, K. H., Abbafati, C., Abbas, K. M., Abd-Allah, F., et al. (2017). Global, regional, and national incidence, prevalence, and years lived with disability for 328 diseases and injuries for 195 countries, 1990-2016: a systematic analysis for the Global Burden of Disease Study 2016. Lancet 390, 1211–1259. GBD 2016 Disease and Injury Incidence and Prevalence Collaborators. doi:10.1016/S0140-6736(17)32154-2

Wang, R., Shen, X., Xing, E., Guan, L., and Xin, L. (2013). Scutellaria baicalensis stem-leaf total flavonoid reduces neuronal apoptosis induced by amyloid beta-peptide (25–35). Neural Regen. Res. 8, 1081–1090. doi:10.3969/j.issn.1673-5374.2013.12.003

Wang, Z. L., Wang, S., Kuang, Y., Hu, Z. M., Qiao, X., and Ye, M. (2018). A comprehensive review on phytochemistry, pharmacology, and flavonoid biosynthesis of Scutellaria baicalensis. Pharm. Biol. 56, 465–484. doi:10.1080/13880209.2018.1492620

World Health Organization (Who), (2017). Depression and other common mental disorders global health estimates . Geneva, Switzerland: World Health Organization .

Google Scholar

World Health Organization (Who), Depression . Geneva, Switzerland: World Health Organization . 2017.

Xiong, Z., Jiang, B., Wu, P.-F., Tian, J., Shi, L. L., Gu, J., et al. (2011). Antidepressant effects of a plant-derived flavonoid baicalein involving extracellular signal-regulated kinases cascade. Biol. Pharm. Bull. 34, 253–259. doi:10.1248/bpb.34.253

Yoon, E. J., Lee, M. Y., Choi, B. I., Lim, K. J., Hong, S. Y., and Park, D. (2020). Pharmaceutical Advantages of GenoTX-407, A Combination of Extracts from Scutellaria baicalensis Root and Magnolia officinalis Bark. Antioxidants (Basel) 9 (11). doi:10.3390/antiox9111111

Zhang, K., He, M., Wang, F., Zhang, H., Li, Y., Yang, J., et al. (2019). Revealing antidepressant mechanisms of baicalin in hypothalamus through systems approaches in corticosterone- induced depressed mice. Front. Neurosci. 13, 834. doi:10.3389/fnins.2019.00834

Zhang, K., Pan, X., Wang, F., Ma, J., Su, G., Dong, Y., et al. (2016). Baicalin promotes hippocampal neurogenesis via SGK1- and FKBP5-mediated glucocorticoid receptor phosphorylation in a neuroendocrine mouse model of anxiety/depression. Sci. Rep. 6, 30951. doi:10.1038/srep30951

Zhang, K., Wang, F., Yang, J.-Y., Wang, L. J., Pang, H. H., Su, G. Y., et al. (2015). Analysis of main constituents and mechanisms underlying antidepressant-like effects of Xiaochaihutang in mice. J. Ethnopharmacol. 175, 48–57. doi:10.1016/j.jep.2015.08.031

Zhang, R., Guo, L., Zhouye, J., Li, X., Zhang, C., Ma, Z., et al. (2018). Radix Scutellariae attenuates CUMS-induced depressive-like behavior by promoting neurogenesis via cAMP/PKA pathway. Neurochem. Res. 43, 2111–2120. doi:10.1007/s11064-018-2635-3

Zhang, R., Ma, Z., Liu, K., Li, Y., Liu, D., Xu, L., et al. (2019). Baicalin exerts antidepressant effects through Akt/FOXG1 pathway promoting neuronal differentiation and survival. Life Sci. 221, 241–248. doi:10.1016/j.lfs.2019.02.033

Zhang, X., Du, L., Zhang, W., Yang, Y., and Zhou, Q. (2017). Therapeutic effects of baicalein on rotenone-induced Parkinson’s disease through protecting mitochondrial function and biogenesis. Sci. Rep. 7, 9968. doi:10.1038/s41598-017-07442-y

Zhao, J., Lu, S., Yu, H., Duan, S., and Zhao, J. (2018). Baicalin and ginsenoside Rb1 promote the proliferation and differentiation of neural stem cells in Alzheimer’s disease model rats. Brain Res. 1678, 187–194. doi:10.1016/j.brainres.2017.10.003

Zhao, Q., Chen, X.-Y., and Martin, C. (2016). Scutellaria baicalensis, the golden herb from the garden of Chinese medicinal plants. Sci. Bull. (Beijing) 61, 1391–1398. doi:10.1007/s11434-016-1136-5

Zhao, T., Tang, H., Xie, L., Zheng, Y., Ma, Z., Sun, Q., et al. (2019). Scutellaria baicalensis Georgi. (Lamiaceae): a review of its traditional uses, botany, phytochemistry, pharmacology and toxicology. J. Pharm. J. Pharmacol. 71, 1353–1369. doi:10.1111/jphp.13129

Zhao, X., Kong, D., Zhou, Q., Wei, G., Song, J., Liang, Y., et al. (2021). Baicalein alleviates depression-like behavior in rotenone-induced Parkinson's disease model in mice through activating the BDNF/TrkB/CREB pathway. Biomed. Pharmacother. 140, 111556. doi:10.1016/j.biopha.2021.111556

Zhao, Y., Zhang, L., Wu, Y., Dai, Q., Zhou, Y., et al. (2018). Selective anti-tumor activity of wogonin targeting the Warburg effect through stablizing p53. Pharmacol. Res. 135, 49–59. doi:10.1016/j.phrs.2018.07.011

Zhong, J., Li, G., Xu, H., Wang, Y., and Shi, M. (2019). Baicalin ameliorates chronic mild stress-induced depression-like behaviors in mice and attenuates inflammatory cytokines and oxidative stress. Braz J. Med. Biol. Res. 52, e8434. doi:10.1590/1414-431X20198434

Zhou, Y., Yang, Z.-Y., and Tang, R.-C. (2016). Bioactive and UV protective silk materials containing baicalin-The multifunctional plant extract from Scutellaria baicalensis Georgi. Mater Sci. Eng. C Mater Biol. Appl. 67, 336–344. doi:10.1016/j.msec.2016.05.063

Keywords: scutellaria baicalensis, depression, preclinical study, meta analysis, systematic review

Citation: Ma Y, Zhou X, Zhang F, Huang C, Yang H, Chen W and Tao X (2024) The effect of scutellaria baicalensis and its active ingredients on major depressive disorder: a systematic review and meta-analysis of literature in pre-clinical research. Front. Pharmacol. 15:1313871. doi: 10.3389/fphar.2024.1313871

Received: 27 October 2023; Accepted: 23 February 2024; Published: 20 March 2024.

Reviewed by:

Copyright © 2024 Ma, Zhou, Zhang, Huang, Yang, Chen and Tao. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Wansheng Chen, [email protected] ; Xia Tao, [email protected]

† These authors share first authorship

Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.

  • Systematic Review
  • Open access
  • Published: 22 March 2024

Clinical characteristics, diagnosis, treatment, and outcome of patients with liver abscess due to Aspergillus spp: a systematic review of published cases

  • Igor Dumic 1 , 2 ,
  • Enzo Marasco Caetano 3 ,
  • Sidney Marcel Domingues 3 ,
  • Ivana Pantic 4 ,
  • Milan Radovanovic 1 , 2 ,
  • Libardo Rueda Prada 1 , 5 ,
  • Charles W Nordstrom 1 , 2 ,
  • Marina Antic 1 , 2 ,
  • Tamara Milovanovic 4 , 6 ,
  • Magdalena Kotseva 7 ,
  • Amteshwar Singh 8 &
  • Shweta FNU 1 , 9  

BMC Infectious Diseases volume  24 , Article number:  345 ( 2024 ) Cite this article

Metrics details

Aspergillus spp liver abscess is a relatively rare entity and thus far no systematic review has been performed examining patients’ demographics, clinical manifestations, diagnosis, management, and outcome.

We performed a systematic review of the literature using MEDLINE and LILACS databases. We searched for articles published in the period from January 1990 to December 24, 2022, to identify patients who developed liver abscesses due to Aspergillus spp.

Our search yielded 21 patients all of whom had invasive aspergillosis confirmed on liver biopsy. Of these patients 81% were adults, and 60% were males. The majority (86%) of patients were immunocompromised and 95% had symptomatic disease at the time of diagnosis. The most common symptoms were fever (79%), abdominal pain (47%), and constitutional symptoms (weight loss, chills, night sweats, fatigue) (38%). Liver enzymes were elevated in 50%, serum galactomannan was positive in 57%, and fungal blood cultures were positive in only 11%. Co-infection with other pathogens preceded development of apsergillosis in one-third of patients, and the majority of the abscesses (43%) were cryptogenic. In the remaining patients with known source, 28% of patients developed liver abscess through dissemination from the lungs, 19% through the portal vein system, and in 10% liver abscess developed through contiguous spread. The most common imaging modality was abdominal computerized tomography done in 86% of patients. Solitary abscess was present in 52% of patients while 48% had multiple abscesses. Inadequate initial empiric therapy was prescribed in 60% of patients and in 44% of patients definite treatment included combination therapy with two or more antifungal agents. Percutaneous drainage of the abscesses was done in 40% of patients, while 20% required liver resection for the treatment of the abscess. Overall mortality was very high at 38%.

Further studies are urgently needed for a better understanding of pathophysiology of liver aspergillosis and for developement of newer blood markers in order to expedite diagnosis and decrease mortality.

Peer Review reports

A liver abscess (LA) is a rare condition characterized by the formation of a purulent cavity by microorganisms in the liver [ 1 , 2 , 3 , 4 , 5 ]. LA is classified as bacterial, protozoan (amoebic), or fungal [ 1 , 2 , 3 , 4 , 5 ]. The most common causes of bacterial (pyogenic) liver abscesses (BLA) are Escherichia coli , Klebsiella spp , Streptococcus anginosus group, Staphylococcus aureus , and anaerobes. Amebic liver abscesses (ALA) are the most common manifestation of extra-intestinal amebiasis caused by Entamoeba histolytica .Fungal pathogens, however, are comparitively rare cause of LA [ 1 , 2 , 3 , 4 , 5 ].

The incidence of BLA varies by geography. For example, in the North American population the incidence is around 2 per 100,000, but 17.6 per 100,000 inhabitants in Taiwan. Meanwhile in Sweden, the incidence of BLA has increased almost three fold over the last decade, from 1.8/100,000 person-years in 2011 to 5.2/100,000 person-years in 2020 which is partially explained by their aging population [ 6 ].

Fungal infections in the liver are less common compared to BLA. Candida spp and Aspergillus spp are the most common causative agents in patients with hematological malignancy [ 7 , 8 , 9 , 10 , 11 , 12 ]. The incidence of these infections has decreased due to the use of antifungal prophylaxis, particularly amongst patients with cancer on immunosuppressive therapy. The most common Aspergillus spp causing infections in humans are: A. fumigatus , A. flavus , A. niger, and A. terreus [ 7 , 8 ]. The most common and most severe form of aspergillosis is invasive aspergillosis (IA), followed by a chronic, allergic form termed chronic bronchopulmonary aspergillosis [ 9 , 10 , 11 , 13 ]. While the lungs and upper respiratory organs are most commonly affected in aspergillosis, other visceral organs are typcially infected following dissemination from the primary lung focus [ 9 , 10 ].

Aspergillus spp liver abscess or invasive liver aspergillosis (ILA) is a rare extrapulmonary manifestation of IA [ 14 ]. In a recent autopsy study, the liver was amongst the least commonly affected extrapulmonary sites, and hepatic aspergillosis was found in only 10% of patients with fatal IA compared to central nervous system and cardiac IA that were the most common extrapulmonary sites involved, in 24% of cases each [ 15 ]. There is a paucity of evidence about patients’ characteristics, risk factors, management, and outcomes of patients with ILA. The data we have about this rare clinical manifestation of IA are based on case reports, case series, and expert opinions. Due to the rarity of the disease, there are no retrospective or prospective studies on this specific topic. Therefore, we performed a scoping review of case reports and case series to understand more about ILA and discuss our findings in the context of established knowledge on the more common etiologies of liver abscesses(i.e.,BLA and ALA.)

A scoping review of the literature was performed by searching the MEDLINE database via PubMed search engine and Latin American and Caribbean Health Sciences Literature (LILACS) database via Bvsalud search engine from January 1990 to December 24, 2022, in order to identify patients who developed liver abscess due to Aspergillus spp using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) extension for scoping review (ScR) methodology. The keywords used for the literature search were: “aspergillus or aspergillosis”, “liver or hepatic”, and “infection or abscess”. Furthermore, the reference list of identified articles was manually screened to identify additional cases that can be included in our analysis.

Two authors (I.D. and E.M.) independently and blindly screened the titles, abstracts, and full manuscripts of the identified articles reporting cases of microbiologically proven ILA. Articles that were not case reports and did not report aspergillosis, articles written in a language other than English and Portuguese, and articles that did not contain sufficient information were excluded. Any discrepancies or uncertainties were resolved by the first author (I.D.).

A total of 1213 articles were identified by the initial search, out of which 14 were duplicates.. The selection process resulted in a total of 21 articles in this study [ 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ]. A detailed PRISMA flowchart is illustrated in Fig. 1 .

figure 1

Prisma flowchart detailing the search results

After the final articles were selected, data was collected and the following variables were extracted: age, gender, comorbidities/immunosuppression (high dose steroids, concurrent or recent chemotherapy in the past 1 year, solid organ transplant [SOT] or hematopoietic stem cell transplant [HSCT], hematologic malignancy - not achieved remission, Acquired Immunodeficiency Syndrome [AIDS], use of Tumor Necrosis Factor [TNF] alpha or anti-CD20 therapy in past 2 years, diabetes mellitus [DM]), presence of any other infections, primary Aspergillus focus and portal of entry, symptoms of abdominal pain, fever, or constitutional symptoms (weight loss, chills, night sweats, fatigue), laboratory findings (liver function tests [LFTs], serum galactomannan [GM], liver biopsy, cultures), imaging, management, and outcome.

All cases included met criteria for definite IA by liver biopsy specimen either demonstrating fungal hyphae and/or fungal cultures growing Aspergillus spp. [ 10 , 36 ].

Demographic characteristics

The total number of cases identified in this scoping review was 21 patients, out of which 17 were adults. The mean age was 38 ± 19 years. Out of 4 pediatric cases, two were males and one was female, while sex was not reported in one child. Immunosuppression was present in 86% of these patients; most commonly due to chemotherapy and hematological malignancy – not achieved remission (35%), followed by organ transplants (20%), while other immune-compromising conditions such as AIDS, aplastic anemia, and splenectomy were less common. For the pediatric group, 3 out of 4 had inherited immunodeficiencies ( Table 1 ).

Source of infection and coinfection

The abscesses were cryptogenic in 43% of cases. A presumed pulmonary source of infection with secondary liver involvement by hematogenous dissemination was documented in 28% of cases. Liver infection by dissemination from the gastrointestinal tract via the portal vein system was documented in in 19%. In the remaining 10%, spread to liver occured contiguously through the skin from right-sided rib osteomyelitis and from partially treated left adrenal gland aspergillosis. Co-infection with another pathogen was present in 33% of cases.

Clinical presentation

Symptomatic disease was present in 95% of cases, while in a single case (5%), the disease was asymptomatic and discovered by serial monitoring of galactomannan test in a post-HSCT patient. The most commonly reported symptoms included fever, abdominal pain, and constitutional symptoms in 79%, 47%, and 38% of patients, respectively ( Table 1 ).

Laboratory findings

All 21 patients had a liver biopsy with Aspergillus spp demonstrated from the liver tissue that met the criteria for confirmed invasive aspergillosis. There was a high variability of reported laboratory findings and many case reports had not reported their full spectrum of laboratory investigation. Furthermore, as many patients were on chemotherapy or in the post-transplant period, complete blood cell counts were frequently affected by the primary problem. LFTs were reported in 14 cases and of those, 50% cases reported liver enzyme elevation. Serum GM and blood cultures were not reported in many cases. In those who reported it, serum GM was positive in 57%. Fungal blood cultures for Aspergillus were positive in only 1 of 9 patients (positivity rate of 11%).

The most common imaging modality was abdominal computerized tomography (CT) performed in 81% of patients at any point during the management.Abdominal ultrasound (US), as an initial test, was performed in 42% of patients. Abdominal magnetic resonance imaging (MRI) was done in only one patient. Abscesses were solitary in 52% of patients, while multiple abscesses were reported in 48%. The abscess size was variable and ranged from 2.2 cm to 9 cm in diameter.

Initial empiric antimicrobial treatment was inadequate in 60% of patients where a bacterial pathogen was suspected and Aspergillus-specific antimicrobial treatment was given only after the cultures were reported. In 53% of patients, monotherapy with either amphotericin, itraconazole, voriconazole, or caspofungin was utilized, while in the remaining 47% combination therapy with any of the two agents was used.

Overall mortality was substantial and death due to complications from overwhelming infection or related complications occurred in 8 out of 21 patients (38%), prior to the diagnosis being established or during the treatment course.

Demographics, comorbidities and the risk factors

Similar to BLA and ALA, ILA occurred more frequently in men. It remains unclear why liver abscesses are more common in men, but across the studies that seems to be a consistent finding regardless of the etiology of liver abscess [ 2 , 4 , 5 ]. In patients with ALA, this noticeable discrepancy could be explained by several mechanisms, including the effect of testosterone, and by alcohol consumption which is traditionally more prominent in men. In cases of E. histolytica infection, alcohol consumption could contribute to higher infection rates since it has been hypothesized that locally produced alcoholic drinks in endemic regions (e.g., palm tree wine) can contain a significant amount of E. histolytica [ 2 , 37 ]. 

A recent study from Sweden demonstrated that BLA incidence has increased over the last decade, and this was attributed to their aging population [ 6 ]. Older age is considered a risk factor for BLA but not for ILA. In our review, the mean age was 38 years which is much younger than 65 years as reported in previous studies on BLA, yet similar to the mean age of patients with ALA of 41 years [ 2 , 4 , 5 , 38 ]. The reason why ILA is a disease of a younger population is probably related to the predispostion of lymphoma and leukemia for this popluation, and organ transplant recipients tend to be younger.

The risk factors for BLA, ALA, and ILA are vastly different ( Table 2 ). The most recognized risk factors for the development of BLA are advanced age, uncontrolled DM, liver trauma, intraabdominal surgery, use of proton pump inhibitors (PPI), and biliary pathology [ 2 , 4 , 5 , 39 ]. The most important risk factors for amebic liver abscesses (ALA) are poor sanitation, travel to endemic areas, and malnutrition [ 2 ] . In contrast, patients with fungal liver abscess are usually profoundly immunocompromised as evidenced by these review findings. The risk factor for hepatosplenic candidiasis, including liver abscess, is prolonged and severe neutropenia [ 40 ]. Only 3 patients in our review were immunocompetent. In these patients, aspergillosis developed during complications of postpartum necrotizing fascitis [ 20 ],as a consequence of gastric ulcer perforation which communicated with the left liver lobe [ 28 ], or from contiguous spread from adrenal gland aspergillosis [ 41 ]. All other patients (86%) were in an immunocompromised state: either HSCT or SOT recipients, or patients who were undergoing high intensity chemotherapy for hematologic malignancies (leukemia and lymphoma). Prolonged neutropenia is a strong risk factor for Aspergillus spp infection in patients with hematologic malignancies [ 42 ]. Children who developed ILA typically had a profound inherited immunodeficiency in the form of chronic granulomatous disease (CGD), purine nucleoside phosphorylase deficiency (PNP), or common variable immunodeficiency (CVID) [ 22 , 23 , 29 ].

Other recently described risk factors for IA include intensive care unit (ICU) stay and preceding bacterial or viral infection [ 43 , 44 , 45 ]. In this review, 33% of patients had co-infection with another pathogen around the time of liver aspergillosis diagnosis. These co-infections are likely additional risk factors which contribute to development of IA through epithelial damage, allowing for easier dissemination of aspergillosis. In fact, up to 60% of patients diagnosed with invasive pulmonary aspergillosis in an autopsy series were found to have co-infection with another pathogen [ 15 ], however in this review it was 33%.

Pathogenesis of liver aspergillosis

Aspergillus is a ubiquitous environmental fungus. While it is a harmless colonizer for the majority of immunocompetent people, it is an opportunistic pathogen in people with defects in cellular and/or humoral immunity. Most IA involves the lungs with inhalation of spores as the most common portal of entry, whereas the visceral organs are usually affected by hematogenous dissemination. Following the lungs, the most common affected organs are the paranasal sinuses and the brain [ 11 , 13 , 46 ]. The liver is very rarely affected in aspergillosis, although some autopsy reports suggest that gastrointestinal (including liver) aspergillosis might be underreported [ 17 , 47 ].

Of the 21 patients with ILA described here, 28% had disease due to hematogenous seeding from the infectious foci in the lungs, while in 19% of cases the portal of entry was presumed to be the gastrointestinal tract. A gastrointestinal portal of entry has been hypothesized to occur due to profound neutropenia, mucositis and damage to the intestinal epithelium during chemotherapy which allows the fungus to migrate and seed into the liver [ 17 ] or due to disruption of intestinal barries during intraabdominal surgery as illustrated in remaining 3 cases [ 16 , 20 , 28 ]. In these cases patients had abdominal surgery for various reasons (perforated peptic ulcer, necrotizing facitis following Cesarean section, and liver transplant) and developed liver abscess 2–4 weeks after that. Cryptogenic liver abscesses were the most commonly documented in 43% in cases where no portal of entry could be identified. Given its angioinvasive features, it is not surprising that the majority of extrapulmonary aspergillosis results from hematogenous dissemination. In two patients the infection occured through contiguous spread from the rib osteomyelitis and from left adrenal gland aspergilosis [ 41 ].

Clinical characteristics and laboratory analysis

Patients with BLA usually present with fever, leukocytosis, and abdominal pain ( Table 2 ). Patients with ALA are more likely to present with nausea, diarrhea, and protracted constitutional symptoms [ 48 ]. Patients with ILA, however, may present differently. Due to profound immunosuppression, these patients are less likely to mount a leukocytosis [ 49 ]. Fever, however, remains the most common, and sometimes the only, sign of the infection.This is particularly true in patients with prolonged and severe neutropenia (absolute neutrophil count of less than 0.5 × 10 9 /L (< 500/μL),). Although less common than in patients with BLA, we found fever to be the most common sign of infection in patients with ILA, occuring in 79%. Abdominal pain was present in 47% of cases and we found constitutional symptoms to be present in 38%. Of note, in some immunocompetent patients the liver can be affected diffusely by a disseminated form of aspergillosis with morphologic features of granuloma rather than a well-formed abscess [ 50 ]. Liver enzymes were reported in 50% of the 14 cases that reported this information, and all of these patients had mild to moderate elevation in transaminases with hepatocellular pattern of liver injury. Cholestatic pattern of liver injury was not observed in any of the patients who reported the liver function test and one patient had mixed patter of liver injury.

A definite diagnosis of IA is established by demonstrating fungal hyphae in tissue specimens or by demonstrating Aspergillus spp. growth in fungal cultures of liver tissue. In this review, we included only case reports and case series that fulfilled this definition. Other laboratory (serum GM, beta D glucan, fungal blood cultures) and imaging findings might assist in establishing diagnosis but are not sufficient [ 10 , 51 ].

The reported sensitivity of serum GM antigen index can vary from 30 to 100%, and specifity is generally reported as > 75%. These values vary significantly between Aspergillus and non- Aspergillus fungi, testing assay, and host factors such as age and prior HSCT or SOT. While galactomannan is relased into serum from the cell wall of replicating Aspergillus species, it is also present in the cell wall of several other fungi and can cross react with antibiotics such as piperacillin-tazobactam and amoxicillin-clavulanate. A low yield from fungal blood cultures is true for other fungal pathogens too, for example Candida spp where sensitivity of blood cultures is limited, and up to 70% of patients with hepatosplenic candidiasis might not have documented fungemia [ 52 , 53 ].

The findings from this report with regard to the serum GM test and fungal blood cultures must be interpreted with caution since many authors of these case reports had not reported the results of these tests. However, if we take into account only the cases that reported results, a positive serum GM was seen in 57% of patients, and fungal blood cultures were positive in 11%. This is in alignment with reports from the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) [ 51 ] which state that the serum GM test is more sensitive than fungal blood culture for the diagnosis of invasive aspergillosis. In one case report from Italy, the diagnosis was challenging when the clinical and radiological findings mimicked hepatosplenic candidiasis. In this instance, the diagnosis was established initially by assessment of Aspergillus specific T cells by an enzyme-linked immunospot (ELISPOT) assay that demonstrated a high number of Aspergillus-specific T cells producing interleukin-10 [TH2(IL-10)] and a low number of Aspergillus-specific T cells producing gamma interferon [TH1(IFN-γ)] [ 33 ]. In this case, the diagnosis was later confirmed by demonstrating fungal growth in liver biopsy specimen and pathohistology.

While serology can be useful to establish a diagnosis in patients with ALA, for ILA and for BLA serologies do not have reliable diagnostic utility.

For diagnosis of LA, abdominal CT and US are the most commonly utilized diagnostic tools, with high sensitivity (US: 85–95%; CT: 100%) [ 54 ]. ALA are greater in size and more commonly solitary compared to BLA which are more frequently multiple and bilobar [ 55 ]. In this review of ILA, 52% had a solitary abscess and 48% had multiple abscesses.

The guidelines of the Infectious Diseases Society of America [ 10 ] recommend voriconazole as initial therapy for invasive aspergillosis based on randomized clinical trials that demonstrated voriconazole to be more efficient than amphotericin B deoxycholate in relation to survival and clinical improvement (71% vs 58%) [ 10 ]. In the current review, only 3 patients received voriconazole monotherapy, 5 recieved amphotericin monotherapy, and 8 received combination of 2 or more antifungal agents. Of 8 patients who received combination therapy, 5 patients received voriconazole plus echinocandin. Of these 5 patients, 2 died. Combination of voriconazole with echinocandin might provide mortality benefit in certain patient populations [ 56 ]. These discrepancies with IDSA guidelines are due to the majority of the older reports being published prior to 2016 when the latest IDSA guidelines on aspergilosis management were published.

Amongst the 21 patients described in this systematic review, surgical resection of the liver abscess was performed in 20%, while percutaneous drainage was adequate for source control in 40%. This highlights the challanges associated with treatment of liver aspergillosis and emphasizes that medical management alone is frequently insufficient. Whether or not percutaneous catheter drainage of liver abscess improves outcomes in patients with ILA is debatable. While it seems intuitive that faster source control by aspiration or surgical drainage would potentially lead to a better outcome, firm data are lacking. Moreover patients with ILA are often too ill to undergo any type of procedure.

The mortality of liver abscesses as a whole has decreased dramatically over the years [ 2 ]. This improvement in morbidity and mortality is attributed to better and more available imaging techniques, and a larger armementarium of medication available to treat liver abscesses. In our review, the mortality of patients with ILA was 38% which was much higher compared to ALA and BLA ( Table 2 ). This higher mortality is due to inherent risk factors in this patient population who tend to be much sicker, immunocompromised, and more challanging to diagnose. Additionally, in ILA patients, the diagnosis is often delayed and empiric therapy is frequently inadequate.

Limitations

While this study brings important data from summarizing previously published case reports on this rare entity it has notable limitations. First, publication bias is inevitable in this type of review, and we acknowledge this shortcoming. Second, the study sample is relatively small, and not all cases reported all variables of interest. Finally, some of the high-quality case reports might have been missed if they were not published in the journals indexed in the two databases we used, or if they were published in a language other than English or Portuguese.

Conclusions

Patients with liver abscess due to aspergilosis have very high overall mortality, 38%, which is higher than in those with bacterial or amoebic etiology. These patients are often immunocompromised and diagnosis is delayed due to low sensitivity and specificity of diagnostic tests. Further prospective studies are urgently needed to evaluate novel biomarkers that might expedite diagnosis and improve the outcome in this patient population.

Availability of data and materials

All data generated or analysed during this study are included in this published article.

Lardière-Deguelte S, et al. Hepatic abscess: diagnosis and management. J Visc Surg. 2015;152(4):231–43.

Article   PubMed   Google Scholar  

Roediger R, Lisker-Melman M. Pyogenic and amebic infections of the liver. Gastroenterol Clin N Am. 2020;49(2):361–77.

Article   Google Scholar  

Khim G, et al. Liver abscess: diagnostic and management issues found in the low resource setting. Br Med Bull. 2019;132(1):45–52.

Article   CAS   PubMed   PubMed Central   Google Scholar  

Serraino C, et al. Characteristics and management of pyogenic liver abscess: a European experience. Medicine (Baltimore). 2018;97(19):e0628.

Article   PubMed   PubMed Central   Google Scholar  

Nie S, Lin D, Li X. Clinical characteristics and management of 106 patients with pyogenic liver abscess in a traditional Chinese hospital. Front Surg. 2022;9:1041746.

Svensson E, et al. Increasing incidence of pyogenic liver abscess in southern Sweden: a population-based study from 2011 to 2020. Infect Dis (Lond). 2023;55(6):375–83.

Article   CAS   PubMed   Google Scholar  

Gautier M, Normand AC, Ranque S. Previously unknown species of aspergillus. Clin Microbiol Infect. 2016;22(8):662–9.

Where Aspergillosis Comes From. 2021. Available from: https://www.cdc.gov/fungal/diseases/aspergillosis/causes.html .

Thompson GR. 3rd and J.H. Young, aspergillus infections . N Engl J Med. 2021;385(16):1496–509.

Patterson TF, et al. Practice guidelines for the diagnosis and Management of Aspergillosis: 2016 update by the Infectious Diseases Society of America. Clin Infect Dis. 2016;63(4):e1–e60.

Rudramurthy SM, et al. Invasive aspergillosis by aspergillus flavus: epidemiology, diagnosis Antifungal Resistance, and Management. J Fungi (Basel). 2019;5(3)

Ledoux M-P, Herbrecht R. Invasive Pulmonary Aspergillosis. J Fungi. 2023;9(2):131.

Article   CAS   Google Scholar  

Ledoux MP, Herbrecht R. Invasive Pulmonary Aspergillosis. J Fungi (Basel). 2023;9:2.

Google Scholar  

López-Cortés LE, et al. Invasive aspergillosis with extrapulmonary involvement: pathogenesis, clinical characteristics and prognosis. Rev Iberoam Micol. 2012;29(3):139–43.

Mudrakola HV, et al. Autopsy study of fatal invasive pulmonary aspergillosis: often undiagnosed premortem. Respir Med. 2022;199:106882.

Jafarian A, Kasraianfard A, Nassiri-Toosi M. Revision liver transplant for persistent infection and localized aspergillosis after hepatic artery thrombosis. Exp Clin Transplant. 2014;12(4):381–3.

PubMed   Google Scholar  

Chasan R, et al. Primary hepatic aspergillosis following induction chemotherapy for acute leukemia. Transpl Infect Dis. 2013;15(5):E201–5.

Gupta KL, et al. Progression of hepatic aspergillosis following second renal transplantation in a patient with recurrent glomerulonephritis. Indian J Pathol Microbiol. 2012;55(4):580–2.

Yamada R, et al. Successful treatment of aspergillus liver abscesses in a patient with acute monoblastic leukemia using combination antifungal therapy including micafungin as a key drug. Int J Hematol. 2010;91(4):711–5.

Rieder J, et al. Successful management of aspergillus liver abscess in a patient with necrotizing fasciitis. Dig Dis Sci. 2007;52(6):1548–53.

van der Velden WJ, et al. Primary hepatic invasive aspergillosis with progression after rituximab therapy for a post transplantation lymphoproliferative disorder. Ann Hematol. 2006;85(9):621–3.

Mamishi S, et al. A case of invasive aspergillosis in CGD patient successfully treated with amphotericin B and INF-gamma. Ann Clin Microbiol Antimicrob. 2005;4:4.

Trachana M, et al. Case report. Hepatic abscesses due to aspergillus terreus in an immunodeficient child. Mycoses. 2001;44(9–10):415–8.

Mazza D, et al. Survival of a liver graft recipient treated for an aspergillar liver abscess. Clin Infect Dis. 1996;23(4):831–2.

Yu L, Su M, Liu Q. Myelodysplastic syndrome with aspergillus fumigatus infection: a case report and literature review. Radiol Infect Diseases. 2017;4(1):26–8.

Scott CJ, et al. Invasive aspergillus fumigatus associated with liver and bone involvement in a patient with AIDS. Int J Infect Dis. 2007;11(6):550–3.

Lee TY, et al. Hepatic abscess caused by aspergillus fumigatus infection following splenectomy and immunosuppressive therapy. J Formos Med Assoc. 2003;102(7):501–5.

Vairani G, Rebeschini R, Barbazza R. Hepatic and subcutaneous abscesses due to aspergillosis. Initial diagnosis of a case by intraoperative fine needle aspiration cytology. Acta Cytol. 1990;34(6):891–4.

CAS   PubMed   Google Scholar  

Aytekin C, et al. Purine nucleoside phosphorylase deficiency with fatal course in two sisters. Eur J Pediatr. 2010;169(3):311–4.

Poovorawan K, et al. Hepatic lymphoma and splenic aspergillosis mimicking HEPATOSPLENIC abscesses from MELIOIDOSIS in THAILAND. Southeast Asian J Trop Med Public Health. 2016;47(2):223–6.

Filice C, et al. Ultrasonographic and microbiological diagnosis of mycetic liver abscesses in patients with AIDS. Microbiol. 1989;12(1):101–4.

CAS   Google Scholar  

Bai QX, et al. Successful treatment of liver aspergilloma by caspofungin acetate first-line therapy in a non-immunocompromised patient. Int J Mol Sci. 2012;13(9):11063–70.

Potenza L, et al. Assessment of aspergillus-specific T cells for diagnosis of invasive aspergillosis in a leukemic child with liver lesions mimicking hepatosplenic candidiasis. Clin Vaccine Immunol. 2008;15(10):1625–8.

Marotta G, et al. Complete resolution of hepatic aspergillosis after non-myeloablative hematopoietic stem cell transplantation in a patient with acute myeloid leukemia. Hematol. 2005;10(5):383–6.

Gottfredsson M, Steingrímsdóttir H. Disseminated invasive aspergillosis in a patient with acute leukaemia. Acta Biomed. 2006;77(Suppl 2):10–3.

Bassetti M, et al. EORTC/MSGERC definitions of invasive fungal diseases: summary of activities of the intensive care unit working group. Clin Infect Dis. 2021;72(Suppl 2):S121–s127.

Jha AK, et al. Evaluation of factors associated with complications in amoebic liver abscess in a predominantly toddy-drinking population: a retrospective study of 198 cases. JGH Open. 2019;3(6):474–9.

Neill L, et al. Clinical characteristics and treatment outcomes in a cohort of patients with pyogenic and amoebic liver abscess. BMC Infect Dis. 2019;19(1):490.

Wang YP, et al. Proton pump inhibitor use significantly increases the risk of cryptogenic liver abscess: a population-based study. Aliment Pharmacol Ther. 2015;41(11):1175–81.

Chen C-Y, et al. Chronic disseminated candidiasis manifesting as hepatosplenic abscesses among patients with hematological malignancies. BMC Infect Dis. 2019;19(1):635.

Chen L, et al. Adrenal and hepatic aspergillosis in an immunocompetent patient. Infect Dis (Lond). 2015;47(6):428–32.

Fiore M, et al. Liver fungal infections: an overview of the etiology and epidemiology in patients affected or not affected by oncohematologic malignancies. Infect Drug Resist. 2018;11:177–86.

Montrucchio G, et al. Risk factors for invasive aspergillosis in ICU patients with COVID-19: current insights and new key elements. Ann Intensive Care. 2021;11(1):136.

Waldeck F, et al. Influenza-associated aspergillosis in critically-ill patients-a retrospective bicentric cohort study. Eur J Clin Microbiol Infect Dis. 2020;39(10):1915–23.

Mohamed A, Rogers TR, Talento AF. COVID-19 associated invasive pulmonary aspergillosis: diagnostic and therapeutic challenges. J Fungi. 2020;6(3):115.

Stemler J, et al. Diagnosis and treatment of invasive aspergillosis caused by non-fumigatus aspergillus spp. J Fungi. 2023;9(4):500.

Kazan E, et al. A retrospective series of gut aspergillosis in haematology patients. Clin Microbiol Infect. 2011;17(4):588–94.

Singh A, et al. Prevalence of cases of amebic liver abscess in a tertiary care Centre in India: a study on risk factors, associated microflora and strain variation of Entamoeba histolytica. PLoS One. 2019;14(4):e0214880.

McCreery RJ, Florescu DF, Kalil AC. Sepsis in immunocompromised patients without human immunodeficiency virus. J Infect Dis. 2020;222(Supplement_2):S156–65.

Ergene U, et al. Disseminated aspergillosis due to aspergillus Niger in immunocompetent patient: a case report. Case Rep Infect Dis. 2013;2013:385190.

PubMed   PubMed Central   Google Scholar  

Ullmann AJ, et al. Diagnosis and management of aspergillus diseases: executive summary of the 2017 ESCMID-ECMM-ERS guideline. Clin Microbiol Infect. 2018;24(Suppl 1):e1–e38.

van Prehn J, et al. Hepatosplenic candidiasis without prior documented Candidemia: an Underrecognized diagnosis? Oncol. 2017;22(8):989–94.

Kullberg BJ, Arendrup MC. Invasive Candidiasis. N Engl J Med. 2015;373(15):1445–56.

Priyadarshi RN, Kumar R, Anand U. Amebic liver abscess: Clinico-radiological findings and interventional management. World J Radiol. 2022;14(8):272–85.

Jindal A, et al. Management practices and predictors of outcome of liver abscess in adults: a series of 1630 patients from a liver unit. J Clin Exp Hepatol. 2021;11(3):312–20.

Marr KA, et al. Combination antifungal therapy for invasive aspergillosis: a randomized trial. Ann Intern Med. 2015;162(2):81–9.

Download references

Internal funding from Mayo Clinic.

Author information

Authors and affiliations.

Mayo Clinic College of Medicine and Science, Rochester, MN, USA

Igor Dumic, Milan Radovanovic, Libardo Rueda Prada, Charles W Nordstrom, Marina Antic & Shweta FNU

Department of Hospital Medicine, Mayo Clinic Health System, Eau Claire, WI, USA

Igor Dumic, Milan Radovanovic, Charles W Nordstrom & Marina Antic

Municipal University of São Caetano do Sul, Sao Paulo, Brazil

Enzo Marasco Caetano & Sidney Marcel Domingues

Clinic for Gastroenterology and Hepatology, University Clinical Center of Serbia, Belgrade, Serbia

Ivana Pantic & Tamara Milovanovic

Department of Hospital Medicine, Mayo Clinic Jacksonville, Florida, USA

Libardo Rueda Prada

Faculty of Medicine, University of Belgrade, Belgrade, Serbia

Tamara Milovanovic

Internal Medicine Residency Program, Franciscan Health, Olympia Fields, IL, USA

Magdalena Kotseva

Department of Medicine, Johns Hopkins University, Baltimore, MD, USA

Amteshwar Singh

Department of Infectious Diseases, Mayo Clinic Health System, Eau Claire, WI, USA

You can also search for this author in PubMed   Google Scholar

Contributions

Conceptualization: ID, TM, MK, FS. Data collection: ID, ECM. Data analysis: ID, SMD, MR. Writing ID, IP, LRP, MA, AS, FS. Editing CN, FS.

Corresponding author

Correspondence to Igor Dumic .

Ethics declarations

Ethics approval and consent to participate.

Not Applicable.

Consent for publication

Competing interests.

The authors declare no competing interests.

Additional information

Publisher’s note.

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/ . The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/ ) applies to the data made available in this article, unless otherwise stated in a credit line to the data.

Reprints and permissions

About this article

Cite this article.

Dumic, I., Caetano, E.M., Domingues, S.M. et al. Clinical characteristics, diagnosis, treatment, and outcome of patients with liver abscess due to Aspergillus spp: a systematic review of published cases. BMC Infect Dis 24 , 345 (2024). https://doi.org/10.1186/s12879-024-09226-y

Download citation

Received : 12 December 2023

Accepted : 14 March 2024

Published : 22 March 2024

DOI : https://doi.org/10.1186/s12879-024-09226-y

Share this article

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

  • Liver abscess
  • Aspergillus
  • Immunosupression

BMC Infectious Diseases

ISSN: 1471-2334

what are the characteristics of a literature review

IMAGES

  1. How To Write A Literature Review

    what are the characteristics of a literature review

  2. How to write a literature review: Tips, Format and Significance

    what are the characteristics of a literature review

  3. Literature Review: Outline, Strategies, and Examples

    what are the characteristics of a literature review

  4. 15 Literature Review Examples (2024)

    what are the characteristics of a literature review

  5. short literature review template

    what are the characteristics of a literature review

  6. Types Of Literature Review Ppt

    what are the characteristics of a literature review

VIDEO

  1. Review of literature

  2. 3_session2 Importance of literature review, types of literature review, Reference management tool

  3. Writing a Literature Review

  4. Part 03: Literature Review (Research Methods and Methodology) By Dr. Walter

  5. Effective Review of Literature

  6. Approaches , Analysis And Sources Of Literature Review ( RESEARCH METHODOLOGY AND IPR)

COMMENTS

  1. How to Write a Literature Review

    Examples of literature reviews. Step 1 - Search for relevant literature. Step 2 - Evaluate and select sources. Step 3 - Identify themes, debates, and gaps. Step 4 - Outline your literature review's structure. Step 5 - Write your literature review.

  2. Writing a Literature Review

    A literature review is a document or section of a document that collects key sources on a topic and discusses those sources in conversation with each other (also called synthesis ). The lit review is an important genre in many disciplines, not just literature (i.e., the study of works of literature such as novels and plays).

  3. What is a Literature Review?

    A literature review is a review and synthesis of existing research on a topic or research question. A literature review is meant to analyze the scholarly literature, make connections across writings and identify strengths, weaknesses, trends, and missing conversations. A literature review should address different aspects of a topic as it ...

  4. How To Write A Literature Review

    1. Outline and identify the purpose of a literature review. As a first step on how to write a literature review, you must know what the research question or topic is and what shape you want your literature review to take. Ensure you understand the research topic inside out, or else seek clarifications.

  5. Introduction

    A literature review is a survey and critical analysis of what has been written on a particular topic, theory, question or method. "In writing the literature review, the purpose is to explore what knowledge and ideas have been established on a topic, what approaches and viewpoints have been adopted, and what are their strengths and weaknesses."

  6. Guidance on Conducting a Systematic Literature Review

    Literature review is an essential feature of academic research. Fundamentally, knowledge advancement must be built on prior existing work. To push the knowledge frontier, we must know where the frontier is. By reviewing relevant literature, we understand the breadth and depth of the existing body of work and identify gaps to explore.

  7. What is a literature review?

    A literature or narrative review is a comprehensive review and analysis of the published literature on a specific topic or research question. The literature that is reviewed contains: books, articles, academic articles, conference proceedings, association papers, and dissertations. It contains the most pertinent studies and points to important ...

  8. What is a Literature Review?

    A literature review is a survey of scholarly sources on a specific topic. It provides an overview of current knowledge, allowing you to identify relevant theories, methods, and gaps in the existing research. There are five key steps to writing a literature review: Search for relevant literature. Evaluate sources. Identify themes, debates and gaps.

  9. 5. The Literature Review

    A literature review may consist of simply a summary of key sources, but in the social sciences, a literature review usually has an organizational pattern and combines both summary and synthesis, often within specific conceptual categories.A summary is a recap of the important information of the source, but a synthesis is a re-organization, or a reshuffling, of that information in a way that ...

  10. Literature Reviews: An Overview of Systematic, Integrated ...

    A literature review is probably the most common academic writing activity that is performed by scholars and graduate students. Imel [] identified a literature review as being either part of a larger study or as a research effort on its own.As a part of a larger study, Imel [] identified the literature is "the foundation for the study."It has been suggested that the literature review for a ...

  11. Ten Simple Rules for Writing a Literature Review

    Literature reviews are in great demand in most scientific fields. Their need stems from the ever-increasing output of scientific publications .For example, compared to 1991, in 2008 three, eight, and forty times more papers were indexed in Web of Science on malaria, obesity, and biodiversity, respectively .Given such mountains of papers, scientists cannot be expected to examine in detail every ...

  12. SOC 001: Introductory Sociology

    The literature review is a critical look at the existing research that is significant to the work that you are carrying out. This overview identifies prominent research trends in addition to assessing the overall strengths and weaknesses of the existing research. ... Characteristics of an effective literature review In addition to fulfilling ...

  13. Approaching literature review for academic purposes: The Literature

    A sophisticated literature review (LR) can result in a robust dissertation/thesis by scrutinizing the main problem examined by the academic study; anticipating research hypotheses, methods and results; and maintaining the interest of the audience in how the dissertation/thesis will provide solutions for the current gaps in a particular field.

  14. Chapter 9 Methods for Literature Reviews

    Literature reviews can take two major forms. The most prevalent one is the "literature review" or "background" section within a journal paper or a chapter in a graduate thesis. This section synthesizes the extant literature and usually identifies the gaps in knowledge that the empirical study addresses (Sylvester, Tate, & Johnstone, 2013).

  15. Types of Literature Reviews

    Literature review: Generic term: published materials that provide examination of recent or current literature. ... Analysis may characterise both literatures and look for correlations between characteristics or use gap analysis to identify aspects absent in one literature but missing in the other: Overview: Generic term: summary of the [medical ...

  16. Literature review

    A literature review is a piece of academic writing demonstrating knowledge and understanding of the academic literature on a specific topic placed in context. A literature review also includes a critical evaluation of the material; this is why it is called a literature review rather than a literature report. It is a process of reviewing the ...

  17. Types of reviews

    "A type of review that has as its primary objective the identification of the size and quality of research in a topic area in order to inform subsequent review" (Booth et al., 2012, p. 269). Characteristics: Main purpose is to map out and categorize existing literature, identify gaps in literature—great for informing policy-making

  18. Six Characteristics of Literature Review

    The first level, exhaustive coverage, means the reviewer intends to be comprehensive in the presentation of works relevant to the topic under consideration. ii. The second type of coverage also ...

  19. The following are the characteristics of good literature review

    A literature review is a scholarly paper that presents the current knowledge including substantive findings as well as theoretical and methodological contributions to a particular topic. Literature

  20. Systematic Review

    A literature review is a type of review that uses a less systematic and formal approach than a systematic review. Typically, an expert in a topic will qualitatively summarize and evaluate previous work, without using a formal, explicit method. ... Results: Including results of the search and selection process, study characteristics, risk of ...

  21. What are the qualities of a good literature review?

    University of Arusha. literature review is a documentation of a comprehensive review of publish and unpublished work from second source of data in the area of specific of the researcher. The ...

  22. Guides: Literature Review Process: Select a Review Type

    Characteristics: A review type mainly used in the social sciences and sciences; usually seen as a standalone review article. Conducted to determine the scope and coverage of literature on a topic; the methods and sources for gathering the literature are made transparent so that the review can be reproduced.

  23. Five tips for developing useful literature summary tables for writing

    Literature reviews offer a critical synthesis of empirical and theoretical literature to assess the strength of evidence, develop guidelines for practice and policymaking, and identify areas for future research.1 It is often essential and usually the first task in any research endeavour, particularly in masters or doctoral level education. For effective data extraction and rigorous synthesis ...

  24. Misinformation, disinformation, and fake news: lessons from an

    Second, based on the systematic literature review, to identify key research gaps and research problems, and thereby give an outlook in terms of avenues for future research. Toward that end, we have performed a systematic review of relevant peer-reviewed journal articles published between 2010 and 2021, based on a quantitative content analysis ...

  25. Characteristics of restricted interests in girls with ASD ...

    The existence of a female phenotype profile in autistic spectrum disorder is one of the current hypotheses to explain the diagnostic discrepancy between men and women. In this context, an international literature review was carried out to evidence and describe the characteristics of restricted interests found in girls with autistic spectrum disorder. A documentary search was conducted on ...

  26. Characteristics of possible mpox reinfection cases: literature review

    Extract. As of September 2023, >90 000 confirmed mpox cases 1 have been reported in 110 countries since the beginning of the worldwide outbreak. In the context of the ongoing outbreak, monkeypox virus (MPXV) is almost exclusively transmitted through intimate skin-to-skin contact, most often through sexual activity. 2 Infection caused by MPXV is expected to provide long-term protection against ...

  27. Scale issues in runoff and sediment delivery (SIRSD): A systematic

    Water erosion, a notorious major threat to food security and ecosystem sustainability, is strongly conditioned by spatial and temporal scale effects. This paper systematically reviews the scale issues in runoff and sediment delivery (SIRSD) as a research field by integrating the traditional review approach and bibliometric analysis. This review summarises SIRSD's roots and the scale effect on ...

  28. Fungemia by Wickerhamomyces anomalus —A Narrative Review

    Indeed, only scarce case reports with literature reviews or small series can be found in the literature [28,29]. The present review aimed to provide data on the epidemiology, antifungal resistance, clinical characteristics, treatment, and outcomes of fungemia by W. anomalus by extracting all the available information from published original ...

  29. Frontiers

    The effect of scutellaria baicalensis and its active ingredients on major depressive disorder: a systematic review and meta-analysis of literature in pre-clinical research. ... characteristics of the animal, including species, number, sex, weight, etc.; (3) the establishment of depression model and anesthesia used in the model; (4 ...

  30. Clinical characteristics, diagnosis, treatment, and outcome of patients

    Aspergillus spp liver abscess is a relatively rare entity and thus far no systematic review has been performed examining patients' demographics, clinical manifestations, diagnosis, management, and outcome. We performed a systematic review of the literature using MEDLINE and LILACS databases. We searched for articles published in the period from January 1990 to December 24, 2022, to identify ...