source of systematic literature review

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Annual Review of Psychology

Volume 70, 2019, review article, how to do a systematic review: a best practice guide for conducting and reporting narrative reviews, meta-analyses, and meta-syntheses.

• Andy P. Siddaway 1 , Alex M. Wood 2 , and Larry V. Hedges 3
• View Affiliations Hide Affiliations Affiliations: 1 Behavioural Science Centre, Stirling Management School, University of Stirling, Stirling FK9 4LA, United Kingdom; email: [email protected] 2 Department of Psychological and Behavioural Science, London School of Economics and Political Science, London WC2A 2AE, United Kingdom 3 Department of Statistics, Northwestern University, Evanston, Illinois 60208, USA; email: [email protected]
• Vol. 70:747-770 (Volume publication date January 2019) https://doi.org/10.1146/annurev-psych-010418-102803
• First published as a Review in Advance on August 08, 2018
• Copyright © 2019 by Annual Reviews. All rights reserved

Systematic reviews are characterized by a methodical and replicable methodology and presentation. They involve a comprehensive search to locate all relevant published and unpublished work on a subject; a systematic integration of search results; and a critique of the extent, nature, and quality of evidence in relation to a particular research question. The best reviews synthesize studies to draw broad theoretical conclusions about what a literature means, linking theory to evidence and evidence to theory. This guide describes how to plan, conduct, organize, and present a systematic review of quantitative (meta-analysis) or qualitative (narrative review, meta-synthesis) information. We outline core standards and principles and describe commonly encountered problems. Although this guide targets psychological scientists, its high level of abstraction makes it potentially relevant to any subject area or discipline. We argue that systematic reviews are a key methodology for clarifying whether and how research findings replicate and for explaining possible inconsistencies, and we call for researchers to conduct systematic reviews to help elucidate whether there is a replication crisis.

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Literature Cited

• APA Publ. Commun. Board Work. Group J. Artic. Rep. Stand. 2008 . Reporting standards for research in psychology: Why do we need them? What might they be?. Am. Psychol . 63 : 848– 49 [Google Scholar]
• Baumeister RF 2013 . Writing a literature review. The Portable Mentor: Expert Guide to a Successful Career in Psychology MJ Prinstein, MD Patterson 119– 32 New York: Springer, 2nd ed.. [Google Scholar]
• Baumeister RF , Leary MR 1995 . The need to belong: desire for interpersonal attachments as a fundamental human motivation. Psychol. Bull. 117 : 497– 529 [Google Scholar]
• Baumeister RF , Leary MR 1997 . Writing narrative literature reviews. Rev. Gen. Psychol. 3 : 311– 20 Presents a thorough and thoughtful guide to conducting narrative reviews. [Google Scholar]
• Bem DJ 1995 . Writing a review article for Psychological Bulletin. Psychol . Bull 118 : 172– 77 [Google Scholar]
• Borenstein M , Hedges LV , Higgins JPT , Rothstein HR 2009 . Introduction to Meta-Analysis New York: Wiley Presents a comprehensive introduction to meta-analysis. [Google Scholar]
• Borenstein M , Higgins JPT , Hedges LV , Rothstein HR 2017 . Basics of meta-analysis: I 2 is not an absolute measure of heterogeneity. Res. Synth. Methods 8 : 5– 18 [Google Scholar]
• Braver SL , Thoemmes FJ , Rosenthal R 2014 . Continuously cumulating meta-analysis and replicability. Perspect. Psychol. Sci. 9 : 333– 42 [Google Scholar]
• Bushman BJ 1994 . Vote-counting procedures. The Handbook of Research Synthesis H Cooper, LV Hedges 193– 214 New York: Russell Sage Found. [Google Scholar]
• Cesario J 2014 . Priming, replication, and the hardest science. Perspect. Psychol. Sci. 9 : 40– 48 [Google Scholar]
• Chalmers I 2007 . The lethal consequences of failing to make use of all relevant evidence about the effects of medical treatments: the importance of systematic reviews. Treating Individuals: From Randomised Trials to Personalised Medicine PM Rothwell 37– 58 London: Lancet [Google Scholar]
• Cochrane Collab. 2003 . Glossary Rep., Cochrane Collab. London: http://community.cochrane.org/glossary Presents a comprehensive glossary of terms relevant to systematic reviews. [Google Scholar]
• Cohn LD , Becker BJ 2003 . How meta-analysis increases statistical power. Psychol. Methods 8 : 243– 53 [Google Scholar]
• Cooper HM 2003 . Editorial. Psychol. Bull. 129 : 3– 9 [Google Scholar]
• Cooper HM 2016 . Research Synthesis and Meta-Analysis: A Step-by-Step Approach Thousand Oaks, CA: Sage, 5th ed.. Presents a comprehensive introduction to research synthesis and meta-analysis. [Google Scholar]
• Cooper HM , Hedges LV , Valentine JC 2009 . The Handbook of Research Synthesis and Meta-Analysis New York: Russell Sage Found, 2nd ed.. [Google Scholar]
• Cumming G 2014 . The new statistics: why and how. Psychol. Sci. 25 : 7– 29 Discusses the limitations of null hypothesis significance testing and viable alternative approaches. [Google Scholar]
• Earp BD , Trafimow D 2015 . Replication, falsification, and the crisis of confidence in social psychology. Front. Psychol. 6 : 621 [Google Scholar]
• Etz A , Vandekerckhove J 2016 . A Bayesian perspective on the reproducibility project: psychology. PLOS ONE 11 : e0149794 [Google Scholar]
• Ferguson CJ , Brannick MT 2012 . Publication bias in psychological science: prevalence, methods for identifying and controlling, and implications for the use of meta-analyses. Psychol. Methods 17 : 120– 28 [Google Scholar]
• Fleiss JL , Berlin JA 2009 . Effect sizes for dichotomous data. The Handbook of Research Synthesis and Meta-Analysis H Cooper, LV Hedges, JC Valentine 237– 53 New York: Russell Sage Found, 2nd ed.. [Google Scholar]
• Garside R 2014 . Should we appraise the quality of qualitative research reports for systematic reviews, and if so, how. Innovation 27 : 67– 79 [Google Scholar]
• Hedges LV , Olkin I 1980 . Vote count methods in research synthesis. Psychol. Bull. 88 : 359– 69 [Google Scholar]
• Hedges LV , Pigott TD 2001 . The power of statistical tests in meta-analysis. Psychol. Methods 6 : 203– 17 [Google Scholar]
• Higgins JPT , Green S 2011 . Cochrane Handbook for Systematic Reviews of Interventions, Version 5.1.0 London: Cochrane Collab. Presents comprehensive and regularly updated guidelines on systematic reviews. [Google Scholar]
• John LK , Loewenstein G , Prelec D 2012 . Measuring the prevalence of questionable research practices with incentives for truth telling. Psychol. Sci. 23 : 524– 32 [Google Scholar]
• Juni P , Witschi A , Bloch R , Egger M 1999 . The hazards of scoring the quality of clinical trials for meta-analysis. JAMA 282 : 1054– 60 [Google Scholar]
• Klein O , Doyen S , Leys C , Magalhães de Saldanha da Gama PA , Miller S et al. 2012 . Low hopes, high expectations: expectancy effects and the replicability of behavioral experiments. Perspect. Psychol. Sci. 7 : 6 572– 84 [Google Scholar]
• Lau J , Antman EM , Jimenez-Silva J , Kupelnick B , Mosteller F , Chalmers TC 1992 . Cumulative meta-analysis of therapeutic trials for myocardial infarction. N. Engl. J. Med. 327 : 248– 54 [Google Scholar]
• Light RJ , Smith PV 1971 . Accumulating evidence: procedures for resolving contradictions among different research studies. Harvard Educ. Rev. 41 : 429– 71 [Google Scholar]
• Lipsey MW , Wilson D 2001 . Practical Meta-Analysis London: Sage Comprehensive and clear explanation of meta-analysis. [Google Scholar]
• Matt GE , Cook TD 1994 . Threats to the validity of research synthesis. The Handbook of Research Synthesis H Cooper, LV Hedges 503– 20 New York: Russell Sage Found. [Google Scholar]
• Maxwell SE , Lau MY , Howard GS 2015 . Is psychology suffering from a replication crisis? What does “failure to replicate” really mean?. Am. Psychol. 70 : 487– 98 [Google Scholar]
• Moher D , Hopewell S , Schulz KF , Montori V , Gøtzsche PC et al. 2010 . CONSORT explanation and elaboration: updated guidelines for reporting parallel group randomised trials. BMJ 340 : c869 [Google Scholar]
• Moher D , Liberati A , Tetzlaff J , Altman DG PRISMA Group. 2009 . Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement. BMJ 339 : 332– 36 Comprehensive reporting guidelines for systematic reviews. [Google Scholar]
• Morrison A , Polisena J , Husereau D , Moulton K , Clark M et al. 2012 . The effect of English-language restriction on systematic review-based meta-analyses: a systematic review of empirical studies. Int. J. Technol. Assess. Health Care 28 : 138– 44 [Google Scholar]
• Nelson LD , Simmons J , Simonsohn U 2018 . Psychology's renaissance. Annu. Rev. Psychol. 69 : 511– 34 [Google Scholar]
• Noblit GW , Hare RD 1988 . Meta-Ethnography: Synthesizing Qualitative Studies Newbury Park, CA: Sage [Google Scholar]
• Olivo SA , Macedo LG , Gadotti IC , Fuentes J , Stanton T , Magee DJ 2008 . Scales to assess the quality of randomized controlled trials: a systematic review. Phys. Ther. 88 : 156– 75 [Google Scholar]
• Open Sci. Collab. 2015 . Estimating the reproducibility of psychological science. Science 349 : 943 [Google Scholar]
• Paterson BL , Thorne SE , Canam C , Jillings C 2001 . Meta-Study of Qualitative Health Research: A Practical Guide to Meta-Analysis and Meta-Synthesis Thousand Oaks, CA: Sage [Google Scholar]
• Patil P , Peng RD , Leek JT 2016 . What should researchers expect when they replicate studies? A statistical view of replicability in psychological science. Perspect. Psychol. Sci. 11 : 539– 44 [Google Scholar]
• Rosenthal R 1979 . The “file drawer problem” and tolerance for null results. Psychol. Bull. 86 : 638– 41 [Google Scholar]
• Rosnow RL , Rosenthal R 1989 . Statistical procedures and the justification of knowledge in psychological science. Am. Psychol. 44 : 1276– 84 [Google Scholar]
• Sanderson S , Tatt ID , Higgins JP 2007 . Tools for assessing quality and susceptibility to bias in observational studies in epidemiology: a systematic review and annotated bibliography. Int. J. Epidemiol. 36 : 666– 76 [Google Scholar]
• Schreiber R , Crooks D , Stern PN 1997 . Qualitative meta-analysis. Completing a Qualitative Project: Details and Dialogue JM Morse 311– 26 Thousand Oaks, CA: Sage [Google Scholar]
• Shrout PE , Rodgers JL 2018 . Psychology, science, and knowledge construction: broadening perspectives from the replication crisis. Annu. Rev. Psychol. 69 : 487– 510 [Google Scholar]
• Stroebe W , Strack F 2014 . The alleged crisis and the illusion of exact replication. Perspect. Psychol. Sci. 9 : 59– 71 [Google Scholar]
• Stroup DF , Berlin JA , Morton SC , Olkin I , Williamson GD et al. 2000 . Meta-analysis of observational studies in epidemiology (MOOSE): a proposal for reporting. JAMA 283 : 2008– 12 [Google Scholar]
• Thorne S , Jensen L , Kearney MH , Noblit G , Sandelowski M 2004 . Qualitative meta-synthesis: reflections on methodological orientation and ideological agenda. Qual. Health Res. 14 : 1342– 65 [Google Scholar]
• Tong A , Flemming K , McInnes E , Oliver S , Craig J 2012 . Enhancing transparency in reporting the synthesis of qualitative research: ENTREQ. BMC Med. Res. Methodol. 12 : 181– 88 [Google Scholar]
• Trickey D , Siddaway AP , Meiser-Stedman R , Serpell L , Field AP 2012 . A meta-analysis of risk factors for post-traumatic stress disorder in children and adolescents. Clin. Psychol. Rev. 32 : 122– 38 [Google Scholar]
• Valentine JC , Biglan A , Boruch RF , Castro FG , Collins LM et al. 2011 . Replication in prevention science. Prev. Sci. 12 : 103– 17 [Google Scholar]
• Article Type: Review Article

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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.

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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.

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.

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Systematic Reviews and Meta Analysis

• Getting Started
• Guides and Standards
• Review Protocols
• Databases and Sources
• Randomized Controlled Trials
• Controlled Clinical Trials
• Observational Designs
• Tests of Diagnostic Accuracy
• Software and Tools
• Where do I get all those articles?
• Collaborations
• EPI 233/528
• Countway Mediated Search
• Risk of Bias (RoB)

Systematic review Q & A

What is a systematic review.

A systematic review is guided filtering and synthesis of all available evidence addressing a specific, focused research question, generally about a specific intervention or exposure. The use of standardized, systematic methods and pre-selected eligibility criteria reduce the risk of bias in identifying, selecting and analyzing relevant studies. A well-designed systematic review includes clear objectives, pre-selected criteria for identifying eligible studies, an explicit methodology, a thorough and reproducible search of the literature, an assessment of the validity or risk of bias of each included study, and a systematic synthesis, analysis and presentation of the findings of the included studies. A systematic review may include a meta-analysis.

For details about carrying out systematic reviews, see the Guides and Standards section of this guide.

Is my research topic appropriate for systematic review methods?

A systematic review is best deployed to test a specific hypothesis about a healthcare or public health intervention or exposure. By focusing on a single intervention or a few specific interventions for a particular condition, the investigator can ensure a manageable results set. Moreover, examining a single or small set of related interventions, exposures, or outcomes, will simplify the assessment of studies and the synthesis of the findings.

Systematic reviews are poor tools for hypothesis generation: for instance, to determine what interventions have been used to increase the awareness and acceptability of a vaccine or to investigate the ways that predictive analytics have been used in health care management. In the first case, we don't know what interventions to search for and so have to screen all the articles about awareness and acceptability. In the second, there is no agreed on set of methods that make up predictive analytics, and health care management is far too broad. The search will necessarily be incomplete, vague and very large all at the same time. In most cases, reviews without clearly and exactly specified populations, interventions, exposures, and outcomes will produce results sets that quickly outstrip the resources of a small team and offer no consistent way to assess and synthesize findings from the studies that are identified.

If not a systematic review, then what?

You might consider performing a scoping review . This framework allows iterative searching over a reduced number of data sources and no requirement to assess individual studies for risk of bias. The framework includes built-in mechanisms to adjust the analysis as the work progresses and more is learned about the topic. A scoping review won't help you limit the number of records you'll need to screen (broad questions lead to large results sets) but may give you means of dealing with a large set of results.

This tool can help you decide what kind of review is right for your question.

Can my student complete a systematic review during her summer project?

Probably not. Systematic reviews are a lot of work. Including creating the protocol, building and running a quality search, collecting all the papers, evaluating the studies that meet the inclusion criteria and extracting and analyzing the summary data, a well done review can require dozens to hundreds of hours of work that can span several months. Moreover, a systematic review requires subject expertise, statistical support and a librarian to help design and run the search. Be aware that librarians sometimes have queues for their search time. It may take several weeks to complete and run a search. Moreover, all guidelines for carrying out systematic reviews recommend that at least two subject experts screen the studies identified in the search. The first round of screening can consume 1 hour per screener for every 100-200 records. A systematic review is a labor-intensive team effort.

How can I know if my topic has been been reviewed already?

Before starting out on a systematic review, check to see if someone has done it already. In PubMed you can use the systematic review subset to limit to a broad group of papers that is enriched for systematic reviews. You can invoke the subset by selecting if from the Article Types filters to the left of your PubMed results, or you can append AND systematic[sb] to your search. For example:

"neoadjuvant chemotherapy" AND systematic[sb]

The systematic review subset is very noisy, however. To quickly focus on systematic reviews (knowing that you may be missing some), simply search for the word systematic in the title:

"neoadjuvant chemotherapy" AND systematic[ti]

Any PRISMA-compliant systematic review will be captured by this method since including the words "systematic review" in the title is a requirement of the PRISMA checklist. Cochrane systematic reviews do not include 'systematic' in the title, however. It's worth checking the Cochrane Database of Systematic Reviews independently.

You can also search for protocols that will indicate that another group has set out on a similar project. Many investigators will register their protocols in PROSPERO , a registry of review protocols. Other published protocols as well as Cochrane Review protocols appear in the Cochrane Methodology Register, a part of the Cochrane Library .

• Next: Guides and Standards >>
• Last Updated: Feb 26, 2024 3:17 PM
• URL: https://guides.library.harvard.edu/meta-analysis

• 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 and Hedges
• Grey Literature
• Managing and 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

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Systematic reviews

• Introduction to systematic reviews
• Steps in a systematic review
• Formulate the question
• Create a protocol (plan)

Sources to search

Bibliographic databases, grey literature and internet sources, other sources.

• Conduct a thorough search
• Post search phase
• Select studies (screening)
• Appraise the quality of the studies
• Extract data, synthesise and analyse
• Interpret results and write
• Guides and manuals
• Training and support

Once the question has been developed the next step is to perform a comprehensive literature search, which aims to identify all relevant literature from a variety of sources.

Finding relevant resources to search for a systematic review

Sources to search:

• Grey literature and internet
• Scanning reference lists from relevant studies
• Searching key journals and conference proceedings (called hand searching)

Snowballing and citation checking

• Contacting study authors, experts, manufacturers, and other organisations

Google Scholar and Google Advanced Search can be useful when searching to find information that is not indexed in databases. However, these should be used to supplement comprehensive searches across scholarly databases, and not instead of them. There are limitations to using these resources:

• Search results are adapted to individual users which impacts the reproducibility of searches
• Google doesn't state what sources are included in a search
• Inefficient export of large numbers of citations to reference management systems
• Large numbers of results mean many researchers may set a limit on the number of results to be screened (e.g. first 200 results or first 5 pages of results)

You can also use a range of search techniques to help you to  focus your searches across Google's resources.

The databases used may vary widely depending on the research question you are trying to find evidence to answer. However here are some good starting points for various disciplines listed below. Note that these recommendations are databases used commonly in systematic reviews in these disciplines, and your project may well have different requirements.

Any health or medical topic:

• MEDLINE (Available on different platforms such as PubMed and Ovid. Essential)
• Embase (Essential)
• CENTRAL (Via the Cochrane Library. Search CENTRAL if the evidence you want to find might have been addressed by randomised or quasi-randomised trials)
• CINAHL (Search CINAHL if your topic has a nursing or allied health aspect to it)
• PsycINFO (Search PsycINFO if your topic has a psychology aspect to it)
• Web of Science/Scopus. Many health systematic reviews will also search one of these multidisciplinary databases for extra thoroughness

Psychology : PsycINFO, MEDLINE, Embase, Web of Science.

Agriculture:  Web of Science, Scopus. Google Scholar could be added to increase comprehensiveness. You might also consider also searching CSIRO Online Journals if your topic has an Australian focus.

Education : ERIC, Education Database, A+ Education, PsycINFO.

Environmental science : Web of Science, Scopus, GreenFILE. Google Scholar could be added to increase comprehensiveness.

Criminology and justice : Criminal Justice Abstracts, NJCRS (National Criminal Justice Reference Service), PsycINFO.

Business, management, accounting : Web of Science, ABI/INFORM, Business Source Complete.

Social sciences : The social sciences are very diverse, so the databases for each project may be quite different. Some databases you could explore might be: Sociological Abstracts, Social Science Database, Scopus, Social Science Research Network (SSRN).

Other disciplines : See the tips for finding relevant databases below.

Tips for finding relevant databases

An excellent way to select databases is to find other systematic reviews on a similar topic to yours and see which databases they have searched

Library subject guides  provide recommended discipline specific information sources that will be useful

UQ Library's  Database search  allows you to find databases appropriate for your research topic

The  technical supplement to the Cochrane Handbook  has a large list of databases for health sciences related topics

UQ Librarians can advise on appropriate databases for your particular research question

How many databases to search

There is no set number of resources to search, only that the search is expansive and comprehensive. Best practice however is to search more than one resource. Systematic reviews in health and medicine will often search 3-5 databases, and searching more is not uncommon.

Video tutorials

Video tutorials for a selection of databases can be found on the Training and support tab

Grey literature is material that has not been made available via a commercial publisher. It’s important to consider whether you’ll need to search grey literature sources for your project. The main consideration is whether you think that the evidence you need to find for your review might actually be found in these types of sources, which will vary widely between research topics and disciplines. For some topics for example online reports might be a key source of evidence, and for others the evidence might only be reasonably expected to be found in published journal articles.

You should consider the requirements of your individual project carefully. Looking at other systematic reviews similar to your proposed review to see what grey literature sources they have searched can be helpful.

Create a plan on searching grey literature to decide upon which resources will be used.

• Identify which types of sources (e.g. conference proceedings, organisational reports etc.) will be relevant for your project
• Decide where you will search for each of these source types, e.g. which search engines, databases, websites. The table above is a good starting point
• Plan how you will search each database, website etc. For example you may need to make simplified searches for some databases, you may use 3 or 4 very simple searches in a search engine like Google etc. If you're unsure of the best approach the UQ Librarians can advise. Making a record of exactly how you will search these databases, websites etc. means you can just report this in your finished review
• Plan how you will manage the results. Many of these databases, websites etc. will have limited functionality. You may have to view the results on-screen, in a downloaded spreadsheet etc.

Report the searches according to PRISMA Guidelines:  Rethlefsen, ML, Kirtley, S, Waffenschmidt, S, et al. PRISMA-S: an extension to the PRISMA Statement for Reporting Literature Searches in Systematic Reviews . Syst Rev. 2021;10(1):39.  

Selecting and searching many of these resources in a systematic, reproducible manner can be tricky. The UQ Librarians can advise. For more in-depth information on grey literature see our Grey Literature guide.

Hand searching

Hand searching means looking through particular journals manually for relevant articles. The principle behind it is that not everything in a journal is indexed in bibliographic databases, and some journals are not covered by these databases. With online journals hand searching is easier in that the journal can be searched with keywords and advanced search tools.

Hand searching should be considered if you suspect that relevant evidence from journals is not being retrieved in your database searches, e.g. you become aware that a particularly relevant journal is not covered adequately by the databases. Hand searching can be slow and time-consuming and will not be required for many projects. For example it is not required for Cochrane Reviews, and Vasser et al. [1] found that a very low percentage of published systematic reviews reported doing hand searching. A review by Cooper et al. [2] provides a very good summary of the evidence around hand searching.

Snowballing (sometimes called reference checking) is the process of examining the references of known documents to identify other relevant literature. In a systematic review it is best practice to check the references of all included studies, so this is typically done after full text screening is completed. The value in this process is to help identify references which may lie outside of traditional indexing resources. Citation databases such as Web of Science and Scopus may be helpful in examining the references of particular papers, or reference lists can be examined manually.

Related to snowballing, forward citation checking means to check the studies that have cited your included studies, again to identify other relevant literature. Forward citation checking is less commonly done than snowballing [3] but is a relatively undemanding way to increase the thoroughness of your project. Citation databases such as Web of Science, Scopus or Google Scholar can be the easiest way to identify papers that have cited a particular paper.

1. Vassar, M, Atakpo, P, Kash, MJ. Manual search approaches used by systematic reviewers in dermatology . J Med Lib Assoc. 2016;104(4):302-304.

2. Cooper, C, Booth, A, Britten, N, Garside, R. A comparison of results of empirical studies of supplementary search techniques and recommendations in review methodology handbooks: a methodological review . Syst Rev. 2017;6(1):234.

3. Briscoe, S, Bethel, A, Rogers, M. Conduct and reporting of citation searching in Cochrane systematic reviews: a cross-sectional study . Res Synth Methods. 2020;11(2):169-180.

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Systematic Review: Home

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Systematic Reviews

What is a systematic review.

A systematic literature review is a method of synthesising scientific evidence and ensuring the quality of this evidence to answer a particular research question transparently and reproducibly. An accurate Systematic review includes all available published outputs on the topic (Guillaume, 2019).

Types systematic review

1. Scoping review A scoping review is a preliminary assessment of the potential size and scope of available research literature. It aims to identify the nature and extent of research evidence (usually including ongoing research).

2. Rapid review Rapid reviews assess what is already known about a policy or practice issue. They use systematic review methods to search for and critically appraise existing research.

3. Narrative review Also called a literature review. It synthesises primary studies and explores this through description rather than statistics. Library support for literature review can be found in this guide.

4. Meta-analysis A meta-analysis statistically combines the results of quantitative studies to provide a more precise effect on the results. This type of study examines data from multiple studies on the same subject to determine trends.

5. Mixed methods/mixed studies Refers to any combination of methods where one significant component is a literature review (usually systematic review).

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• Introduction
• Conclusions
• Article Information

LMIC indicates low- and- middle-income country; SR, systematic review.

a This review included distinct conclusions about separate conditions and comparators, and so it appears in this map more than once.

eAppendix 1. Search Strategies

eAppendix 2. Excluded Studies

eAppendix 3. Evidence Table

eAppendix 4. Conditions in Previously Published Map in 2018 and Current Map

eReferences.

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Mak S , Allen J , Begashaw M, et al. Use of Massage Therapy for Pain, 2018-2023 : A Systematic Review . JAMA Netw Open. 2024;7(7):e2422259. doi:10.1001/jamanetworkopen.2024.22259

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Use of Massage Therapy for Pain, 2018-2023 : A Systematic Review

• 1 Veterans Health Administration, Greater Los Angeles Healthcare System, Los Angeles, California
• 2 UCLA Fielding School of Public Health, University of California, Los Angeles
• 3 RAND Corporation, Santa Monica, California

Question   What is the certainty or quality of evidence in recent systematic reviews for use of massage therapy for painful adult health conditions?

Findings   This systematic review identified 129 systematic reviews in a search of the literature published since 2018; of these, 41 assessed the certainty or quality of evidence of their conclusions. Overall, 17 systematic reviews regarding 13 health conditions were mapped, and most reviews concluded that the certainty of evidence was low or very low.

Meaning   This study found that despite massage therapy having been the subject of hundreds of randomized clinical trials and dozens of systematic reviews about adult health conditions since 2018, there were few conclusions that had greater than low certainty of evidence.

Importance   Massage therapy is a popular treatment that has been advocated for dozens of painful adult health conditions and has a large evidence base.

Objective   To map systematic reviews, conclusions, and certainty or quality of evidence for outcomes of massage therapy for painful adult health conditions.

Evidence Review   In this systematic review, a computerized search was conducted of PubMed, the Allied and Complementary Medicine Database, the Cumulated Index to Nursing and Allied Health Literature, the Cochrane Database of Systematic Reviews, and Web of Science from 2018 to 2023. Included studies were systematic reviews of massage therapy for pain in adult health conditions that formally rated the certainty, quality, or strength of evidence for conclusions. Studies of sports massage therapy, osteopathy, dry cupping or dry needling, and internal massage therapy (eg, for pelvic floor pain) were ineligible, as were self-administered massage therapy techniques, such as foam rolling. Reviews were categorized as those with at least 1 conclusion rated as high-certainty evidence, at least 1 conclusion rated as moderate-certainty evidence, and all conclusions rated as low- or very low–certainty evidence; a full list of conclusions and certainty of evidence was collected.

Findings   A total of 129 systematic reviews of massage therapy for painful adult health conditions were found; of these, 41 reviews used a formal method to rate certainty or quality of evidence of their conclusions and 17 reviews were mapped, covering 13 health conditions. Across these reviews, no conclusions were rated as high certainty of evidence. There were 7 conclusions that were rated as moderate-certainty evidence; all remaining conclusions were rated as low- or very low–certainty evidence. All conclusions rated as moderate certainty were that massage therapy had a beneficial associations with pain.

Conclusions and Relevance   This study found that despite a large number of randomized clinical trials, systematic reviews of massage therapy for painful adult health conditions rated a minority of conclusions as moderate-certainty evidence and that conclusions with moderate- or high-certainty evidence that massage therapy was superior to other active therapies were rare.

Massage therapy is a popular and widely accepted complementary and integrative health modality for individuals seeking relief from pain. 1 This therapy is the practice of manual assessment and manipulation of the superficial soft tissues of skin, muscle, tendon, ligament, and fascia and the structures that lie within the superficial tissues for therapeutic purpose. 2 Individuals may seek massage therapy to address pain where conventional treatments may not always provide complete relief or may come with potential adverse effects. Massage therapy encompasses a range of techniques, styles, and durations and is intended to be delivered by uniquely trained and credentialed therapists. 3 Original research studies have reported on massage therapy delivered by a wide variety of health care professionals, such as physical therapists, physiotherapists, and nurses. 4 , 5 Despite massage therapy’s popularity and long history in practice, evidence of beneficial outcomes associated with massage therapy remains limited.

The Department of Veterans Affairs (VA) previously produced an evidence map of massage therapy for pain, which included systematic reviews published through 2018. 6 An evidence map is a form of systemic review that assesses a broad field to identify the state of the evidence, gaps in knowledge, and future research needs and that presents results in a user-friendly format, often a visual figure or graph. 7 To categorize this evidence base for use in decision-making by policymakers and practitioners, VA policymakers requested a new evidence map of reviews published since 2018 to answer the question “What is the certainty of evidence in systematic reviews of massage therapy for pain?”

This systematic review is an extension of a study commissioned by the VA. While not a full systematic review, this study nevertheless reports methods and results using the Preferred Reporting Items for Systematic Reviews and Meta-analyses ( PRISMA ) reporting guideline where applicable and filed the a priori protocol with the VA Evidence Synthesis Program Coordinating Center. Requirements for review and informed consent were waived because the study was designated as not human participants research.

Literature searches were based on searches used for the evidence map of massage therapy completed in 2018. 8 We searched 5 databases for relevant records published from July 2018 to April 2023 using the search terms “massage,” “acupressure,” “shiatsu,” “myofascial release therapy,” “systematic*,” “metaanaly*,” and similar terms. The databases were PubMed, the Allied and Complementary Medicine Database, the Cumulated Index to Nursing and Allied Health Literature, the Cochrane Database of Systematic Reviews, and Web of Science. See eAppendix 1 in Supplement 1 for full search strategies.

Each title was screened independently by 2 authors for relevance (S.M., J.A., and P.G.S.). Abstracts were then reviewed in duplicate, with any discrepancies resolved by group discussion. To be included, abstracts or titles needed to be about efficacy or effectiveness of massage therapy for a painful adult health condition and be a systematic review with more than 1 study about massage therapy. A systematic review was defined as a review that had a documented systematic method for identifying and critically appraising evidence. In general, any therapist-delivered modality described as massage therapy by review authors was considered eligible (eg, tuina, acupressure, auricular acupressure, reflexology, and myofascial release). Sports massage therapy, osteopathy, dry cupping or dry needling, and internal massage therapy (eg, for pelvic floor pain) were ineligible, as were self-administered massage therapy techniques, like foam rolling. Reviews had to be about a painful condition for adults, and we excluded publications in low- and middle-income countries because of differences in resources for usual care or other active treatments for included conditions. Publications were required to compare massage therapy with sham or placebo massage, usual care, or other active therapies. Systematic reviews that covered other interventions were eligible if results for massage therapy were reported separately.

We next restricted eligibility to reviews that used formal methods to assess the certainty (sometimes called strength or quality) of the evidence for conclusions. In general, this meant using Grading of Recommendations, Assessment, Development, and Evaluations (GRADE). 9 However, other formal methods were also included, such as the approach used by the US Agency for Healthcare Research and Quality (AHRQ) Evidence-based Practice Center (EPC) program. To be included, a review had to state or cite the method used and report the certainty (or strength or quality) of evidence for each conclusion. After we applied this restriction, most health conditions had only 1 systematic review meeting the eligibility criteria, and we used this review for the map. Among conditions for which we identified more than 1 review meeting the eligibility criteria, we first assessed whether reviews differed in some other feature used to classify reviews on our map (eg, different comparators or type of massage therapy), which we would label with the appropriate designation (such as vs usual care or reflexology ). If there were multiple reviews about the same condition and they did not differ in some other feature, we selected the systematic review we judged as being most informative for readers. In general, this was the most recent review or the review with the greatest number of included studies.

Data on study condition, number of articles in a review, intervention characteristics, comparators, conclusions, and certainty, quality, or strength of evidence were extracted by 1 reviewer and then verified by a second reviewer (S.M., J.A., and P.G.S.). Our evidence mapping process produced a visual depiction of the evidence for massage therapy, as well as an accompanying narrative with an ancillary figure and table.

The visual depiction or evidence map uses a bubble plot format to display information on 4 dimensions: bubble size, bubble label, x-axis, and y-axis. This allowed us to provide the following types of information about each included systematic review:

Number of articles in systematic review (bubble size): The size of each bubble corresponds to the number of relevant primary research studies included in a systematic review.

Condition (bubble label): Each bubble is labeled with the condition discussed by that systematic review.

Shapes and colors: Intervention characteristics for each condition are presented in the form of colors (type of intervention) and shapes (comparators). For type of intervention, we included nonspecified massage therapy, tuina, myofascial release, reflexology, acupressure, and auricular acupressure. For comparators, we included mixed comparators with subgroups, mixed comparators with no subgroups, sham or placebo, and active therapy or usual care. A condition can appear more than once if multiple systematic reviews included different type of massage therapy or different comparators.

Strength of findings (rows): Each condition is plotted on the map based on the ratings of certainty of evidence statement as reported in the systematic reviews: high, moderate, low, or very low.

Outcome associated with massage therapy (columns): Each condition is plotted in potential benefit or no benefit as the outcome associated with massage therapy. Columns are not mutually exclusive. A review could have more than 1 conclusion, and conclusions could differ in the benefit associated with massage therapy. Both conclusions are included on the map.

Risk of bias is not part of the method of an evidence map. We assessed the quality of included reviews using criteria developed by the U S Preventive Services Task Force (USPSTF). Certainty of evidence as determined by the original authors of the systematic review was abstracted for each conclusion in each systematic review and tabulated.

The search identified 1164 potentially relevant citations. Among 129 full-text articles screened, 41 publications were retained for further review. Of these, 24 reviews were excluded from the map for the following reasons: only 1 primary study about interventions of interest (11 studies), outcomes associated with massage therapy could not be distinguished from other included interventions (5 studies), not an intervention of interest (3 studies), not a comparison of interest (2 studies), overlap with a more recent or larger review that was already included on the map (2 studies), and self-delivered therapy (1 study). We included 17 publications in this map covering 13 health conditions. 4 , 10 - 25 The literature flowchart ( Figure 1 ) summarizes results of the study selection process, and eAppendix 2 in Supplement 1 presents citations for all excluded reviews at full-text screening.

The total number of primary studies about massage therapy for pain in the included reviews ranged from 2 studies to 23 studies. There were 12 reviews that included fewer than 10 primary studies 4 , 11 - 17 , 20 - 23 and 5 reviews that included 10 to 25 studies about massage therapy for pain. 10 , 18 , 19 , 24 , 25 Of included reviews, 3 reviews were completed by the Cochrane Collaboration 4 , 19 , 23 and 2 reviews were completed by the AHRQ EPC program. 11 , 18

We categorized the included 17 reviews by health condition. These categories were cancer-related pain, 15 , 24 back pain (including chronic back pain, 25 chronic low back pain, 18 , 22 and low back pain 17 ), chronic neck pain, 18 fibromyalgia, 21 labor pain, 4 , 19 mechanical neck pain, 13 myofascial pain, 14 palliative care needs, 10 plantar fasciitis, 12 post–breast cancer surgery pain, 16 postcesarean pain, 23 postpartum pain, 20 and postoperative pain. 11

Of 17 included reviews, 3 reviews included more than 1 type of massage therapy and 14 reviews included 1 type of massage therapy. Reviews by Chou et al 11 and Smith et al 16 included acupressure and nonspecified massage therapy as interventions. The review by Candy et al 7 included reflexology and nonspecified massage therapy as interventions. Of the 14 reviews with 1 type of massage therapy, there were 5 reviews describing nonspecified massage therapy, 10 , 14 , 17 , 20 1 review about tuina, 22 5 reviews about myofascial release, 8 , 9 , 12 , 18 , 19 and 3 reviews about acupressure. 13 , 15 , 21

A variety of comparators were included in reviews. Of 9 reviews that included more than 1 comparator in analyses, 4 , 11 , 13 , 14 , 18 - 22 2 reviews did not conduct separate analyses by comparator (labeled mixed with no subgroups ) 13 , 14 and 3 reviews conducted separate analyses by comparator (labeled mixed with subgroups ). 4 , 21 , 22 The other 4 reviews included a mix of comparators with separate conclusions: sham or placebo and active therapy or usual care, 11 mixed with no subgroups and active therapy or usual care, 18 mixed with subgroups and active therapy or usual care, 20 and mixed with no subgroups, sham, and active therapy or usual care. 19 There were 8 reviews that included 1 comparator only in their analyses, 10 , 12 , 15 - 17 , 23 - 25 with 7 reviews that described interventions compared with active therapy or usual care only, 10 , 12 , 15 , 17 , 23 - 25 while 1 review limited inclusion to primary studies with a sham or placebo comparator. 16

There was substantial variation in the reporting of other details from primary studies in included reviews. Any study that did not specify the mode of delivery was included; studies that explicitly stated that massage therapy was self-delivered were excluded. Of the 17 included reviews, 5 reviews provided details of personnel who administered the therapy, including massage therapist, nurse, aromatherapist, physiotherapist, and reflexologist. 4 , 10 , 19 - 21 A total of 7 reviews presented length of sessions (eg, 5-minute or 90-minute sessions for massage therapy studies and 30-second or 5-minute sessions for acupressure studies). 10 , 16 , 18 , 20 - 23 With the exception of the review by He et al, 15 all reviews reported details about frequency, duration, or both when available. A total of 9 reviews included information about frequency of sessions (eg, 1 session or once every 3 weeks for massage therapy studies and 4 times per day or daily for acupressure studies), 10 , 12 , 16 - 18 , 20 - 23 and 9 reviews reported duration of sessions (eg, single session or 3 months). 10 - 12 , 16 - 18 , 20 , 22 , 23 There were 7 reviews that included details about follow-up (eg, 1 week or 12 months). 10 , 13 , 17 , 18 , 21 , 23 , 25

Using USPSTF criteria to rate the quality of included reviews, 10 reviews were rated good 4 , 10 , 11 , 14 - 16 , 18 , 19 , 21 , 23 and 7 reviews were rated fair. 12 , 13 , 17 , 20 , 22 , 24 , 25 See eAppendix 3 in Supplement 1 for each review’s rating.

Figure 2 is a visual depiction of the following types of information about each included systematic review: condition, types of comparison treatments (shapes), types of massage therapy (color), number of articles included for each conclusion (bubble size), outcomes associated with massage therapy for pain (columns), and certainty of evidence rating (rows). There were 6 reviews mapped more than once, reflecting primary studies describing more than 1 health condition, 18 more than 1 type of massage therapy, 10 , 20 or outcomes associated with massage therapy compared with different comparators. 11 , 17 - 19 There were 7 conditions from reviews 14 , 16 - 19 , 21 , 22 that reported 1 conclusion rated as moderate-certainty evidence, all of which concluded that massage therapy was associated with beneficial outcomes for pain ( Table 1 ). However, most other conditions had conclusions rated as low- or very low–certainty evidence (12 reviews about 10 conditions 4 , 10 - 13 , 15 , 17 - 20 , 23 - 25 ). This rating means “Our confidence in the effect estimate is limited. The true effect may be substantially different from the estimate of effect,” or “We have very little confidence in the effect estimate.” See eAppendix 3 in Supplement 1 for conclusions in all reviews. This map included 4 conditions that did not appear in the 2018 map, 12 , 16 , 20 , 23 and there were 8 conditions in the 2018 map that did not have new reviews meeting eligibility criteria (mainly a formal grading of the certainty of evidence); 7 health conditions 10 , 11 , 13 - 15 , 17 , 18 , 21 , 22 , 24 , 25 were included in the 2018 map and the new map (see details in eAppendix 4 in Supplement 1 ).

Evidence about adverse events was collected by approximately half of included reviews, and no serious adverse events were reported. While 11 of 17 reviews 10 , 11 , 13 , 15 , 17 - 19 , 22 - 25 described adverse events, 2 reviews 18 , 23 included certainty of evidence conclusions for adverse events for 3 health conditions ( Table 2 ).

There is a large literature of original randomized clinical trials and systematic reviews of randomized clinical trials of massage therapy as a treatment for pain. Our systematic review found that despite this literature, there were only a few conditions for which authors of systematic reviews concluded that there was at least moderate-certainty evidence regarding health outcomes associated with massage therapy and pain. Most reviews reported low- or very low–certainty evidence. Although adverse events associated with massage therapy for pain were rare, the evidence was limited. For reviews that had conclusions about adverse events, authors were uncertain if there was a difference between groups or did not find a difference between groups and rated the evidence low to very low certainty of evidence.

Massage therapy is a broad term that is inclusive of many styles and techniques. We applied exclusion criteria determined a priori to help identify publications for inclusion in the evidence map. Despite that procedure, there was still a lack of clarity in determining what massage therapy is. For instance, acupressure was sometimes considered acupuncture and other times considered massage therapy, depending on author definition. In this case, we reviewed and included only publications that were explicitly labeled acupressure and did not review publications about acupuncture only. This highlights a fundamental issue with examining the evidence base of massage therapy for pain when there is ambiguity in defining what is considered massage therapy.

Unlike a pharmaceutical placebo, sham massage therapy may not be truly inactive. It is conceivable that even the light touch or touch with no clear criterion 26 used in sham massage therapy may be associated with some positive outcomes, meaning that patients who receive the massage therapy intervention and those who receive a sham massage therapy could both demonstrate some degree of symptom improvement. Limitations of sham comparators raise the question of whether sham or placebo treatment is an appropriate comparison group in massage therapy trials. It may be more informative to compare massage therapy with other treatments that are accessible and whose benefits are known so that any added beneficial outcomes associated with massage therapy could be better isolated and understood.

Compared with the 2018 map, our map included 4 new conditions not on the 2018 map, while 8 conditions from the 2018 map had no new reviews meeting eligibility criteria and 7 health conditions appeared in both maps. Despite identifying new conditions and conclusions with higher certainty of evidence in several reviews in our updated search, most included reviews reported low or very low certainty of evidence, suggesting that the most critical research need is for better evidence to increase certainty of evidence for massage therapy for pain. This is a challenge given that massage, like other complementary and integrative health interventions, does not have the historical research infrastructure that most health professions have. 27 Nevertheless, it is only when systematic reviews and meta-analyses are conducted with high-quality primary studies that the association or lack of association of massage therapy with pain will reach higher certainties of evidence. Studies comparing massage therapy with placebo or sham are probably not the priority; rather, the priority should be studies comparing massage therapy with other recommended, accepted, and active therapies for pain. Studies comparing massage therapy with other recommended therapies should also have a sufficiently long follow-up to allow any nonspecific outcomes (eg, those associated with receiving some new treatment) to dissipate. For example, this period has been proposed to be at least 6 months for studies of chronic pain.

There are 2 main limitations to this systematic review’s evidence map. The first, common to all systematic reviews, is that we may not have identified all potentially eligible evidence. If a systematic review was published in a journal not indexed in any of 5 databases we searched and we did not identify it as part of our search of references of included publications, then we would have missed it. Nevertheless, our search strategy identified more than 200 publications about massage therapy for pain published since July 2018, so we did not lack potential reviews to evaluate. The second limitation of evidence maps is that we did not independently evaluate the source evidence; in other words, we took conclusions of authors of the systematic review at face value. That is the nature of an evidence map. Particular to this application of the mapping process, we mapped the review we deemed most informative for the 2 health conditions that had more than 1 eligible review (back pain and labor pain). This necessarily requires judgment, and others could disagree with that judgment. We included the citation for reviews excluded from the map for this overlap reason in supplemental material, and interested readers can review it for additional information. As in all evidence-based products and particularly in 1 such as this covering a large and complex evidence base, it is possible that there are errors of data extraction and compilation. We used dual review to minimize the chance of such errors, but if we are notified of errors, we will correct them.

Although this systematic review found that the number of conclusions about the effectiveness of massage therapy that were judged to have at least moderate certainty of evidence was greater now than in 2018, it was still small relative to the need. More high-quality randomized clinical trials are needed to provide a stronger evidence base to assess the effect of massage therapy on pain. For painful conditions that do not have at least moderate-certainty evidence supporting use of massage therapy, new studies that address limitations of existing research are needed. The field of massage therapy would be best advanced by educating the wider research community with clearer definitions of massage therapy and whether it is appropriate to include multiple modalities in the same systematic review.

Accepted for Publication: May 15, 2024.

Published: July 15, 2024. doi:10.1001/jamanetworkopen.2024.22259

Open Access: This is an open access article distributed under the terms of the CC-BY License . © 2024 Mak S et al. JAMA Network Open .

Corresponding Author: Selene Mak, PhD, MPH, Veterans Health Administration, Greater Los Angeles Healthcare System, 11301 Wilshire Blvd, Los Angeles, CA 90073 ( [email protected] ).

Author Contributions: Drs Mak and Shekelle had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: Mak, Miake-Lye, Shekelle.

Acquisition, analysis, or interpretation of data: Mak, Allen, Begashaw, Beroes-Severin, De Vries, Lawson, Shekelle.

Drafting of the manuscript: Mak, Allen, Begashaw, Beroes-Severin, De Vries, Lawson, Shekelle.

Critical review of the manuscript for important intellectual content: Mak, Miake-Lye, Shekelle.

Statistical analysis: Allen.

Obtained funding: Shekelle.

Administrative, technical, or material support: Begashaw, Miake-Lye, Beroes-Severin, De Vries, Lawson.

Supervision: Mak, Shekelle.

Conflict of Interest Disclosures: None reported.

Funding/Support: Funding was provided by the Department of Veterans Affairs Health Services Research and Development.

Role of the Funder/Sponsor: The funders had no role in the collection, management, analysis, and interpretation of the data and preparation of the manuscript. The funders participated in the design and conduct of the study, the review and approval of the manuscript, and the decision to submit the manuscript for publication.

Data Sharing Statement: See Supplement 2 .

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A Narrative Review of Literature Examining Studies Researching the Impact of Law on Health and Economic Outcomes

Affiliation.

• 1 Office of Policy, Performance, and Evaluation, Centers for Disease Control and Prevention, Atlanta, Georgia (Drs Pepin, St. Clair Sims, Khushalani, Kelly, Arifkhanova, Puddy, and Kaminski); Office of Public Health Law Services, National Center for State, Tribal, Local, and Territorial Public Health Infrastructure and Workforce, Centers for Disease Control and Prevention, Atlanta, Georgia (Dr Hulkower); and Oak Ridge Institute for Science and Education (ORISE), Oak Ridge, Tennessee (Drs Tonti, Song, and Calhoun).
• PMID: 37797335
• PMCID: PMC10841287 (available on 2025-01-01 )
• DOI: 10.1097/PHH.0000000000001833

Context: Public health policy can play an important role in improving public health outcomes. Accordingly, there has been an increasing emphasis by policy makers on identifying and implementing evidence-informed public health policy interventions.

Program or policy: Growth and refinement of the field of research assessing the impact of legal interventions on health outcomes, known as legal epidemiology, prompted this review of studies on the relationship between laws and health or economic outcomes.

Implementation: Authors systematically searched 8 major literature databases for all English language journal articles that assessed the effect of a law on health and economic outcomes published between January 1, 2009, and September 18, 2019. This search generated 12 570 unique articles 177 of which met inclusion criteria. The team conducting the systematic review was a multidisciplinary team that included health economists and public health policy researchers, as well as public health lawyers with expertise in legal epidemiological research methods. The authors identified and assessed the types of methods used to measure the laws' health impact.

Evaluation: In this review, the authors examine how legal epidemiological research methods have been described in the literature as well as trends among the studies. Overall, 3 major themes emerged from this study: (1) limited variability in the sources of the health data across the studies, (2) limited differences in the methodological approaches used to connect law to health outcomes, and (3) lack of transparency surrounding the source and quality of the legal data relied upon.

Discussion: Through highlighting public health law research methodologies, this systematic review may inform researchers, practitioners, and lawmakers on how to better examine and understand the impacts of legal interventions on health and economic outcomes. Findings may serve as a source of suggested practices in conducting legal epidemiological outcomes research and identifying conceptual and method-related gaps in the literature.

Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.

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Conflict of interest statement

The authors have indicated that they have no potential conflicts of interest to disclose.

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Systematic and other reviews: criteria and complexities

Robert t. sataloff.

1 Editor-in-Chief, Journal of Voice, Philadephia, USA

2 Editor Emeritus, Ear, Nose and Throat Journal, Philadephia, USA

Matthew L. Bush

3 Assistant Editor, Otology & Neurotology, Lexington, USA

Rakesh Chandra

4 Editor-in-Chief, Ear, Ear, Nose and Throat Journal, Nashville, USA

Douglas Chepeha

5 Editor-in-Chief, Journal of Otolaryngology – Head & Neck Surgery, Toronto, Canada

Brian Rotenberg

6 Editor-in-Chief, Journal of Otolaryngology – Head & Neck Surgery, London, Canada

Edward W. Fisher

7 Senior Editor, Journal of Laryngology and Otology, Birmingham, UK

David Goldenberg

8 Editor-in-Chief, Operative Techniques in Otolaryngology – Head and Neck Surgery, Hershey, USA

Ehab Y. Hanna

9 Editor-in-Chief, Head & Neck, Houston, USA

Joseph E. Kerschner

10 Editor-in-Chief, International Journal of Pediatric Otorhinolaryngology, Milwaukee, USA

Dennis H. Kraus

11 Co-Editor-in-Chief, Journal of Neurological Surgery Part B: Skull Base, New York, USA

John H. Krouse

12 Editor-in-Chief, Otolaryngology – Head and Neck Surgery, Philadelphia, USA

13 Editor-in-Chief, OTO-Open, Philadelphia, USA

14 Editor-in-Chief, Journal for Oto-Rhino-Laryngology, Head and Neck Surgery, Philadelphia, USA

15 Editor-in-Chief, World Journal of Otorhinolaryngology – Head and Neck Surgery, Philadelphia, USA

Michael Link

16 Co-Editor-in-Chief, Journal of Neurological Surgery Part B: Skull Base, Rochester, USA

Lawrence R. Lustig

17 Editor-in-Chief, Otology & Neurotology, New York, USA

Samuel H. Selesnick

18 Editor-in-Chief, The Laryngoscope, New York, USA

Raj Sindwani

19 Editor-in-Chief, American Journal of Rhinology & Allergy, Cleveland, USA

Richard J. Smith

20 Editor-in-Chief, Annals of Otology, Rhinology & Laryngology, Iowa City, USA

James Tysome

21 Editor-in-Chief, Clinical Otolaryngology, Cambridge, UK

Peter C. Weber

22 Editor-in-Chief, American Journal of Otolaryngology, Boston, USA

D. Bradley Welling

23 Editor-in-Chief, Laryngoscope Investigative Otolaryngology, Boston, USA

Review articles can be extremely valuable. They synthesize information for readers, often provide clarity and valuable insights into a topic; and good review articles tend to be cited frequently. Review articles do not require Institutional Review Board (IRB) approval if the data reviewed are public (including private and government databases) and if the articles reviewed have received IRB approval previously. However, some institutions require IRB review and exemption for review articles. So, authors should be familiar with their institution’s policy. In assessing and interpreting review articles, it is important to understand the article’s methodology, scholarly purpose and credibility. Many readers, and some journal reviewers, are not aware that there are different kinds of review articles with different definitions, criteria and academic impact [ 1 ]. In order to understand the importance and potential application of a review article, it is valuable for readers and reviewers to be able to classify review articles correctly.

Systematic reviews

Authors often submit articles that include the term “systematic” in the title without realizing that that term requires strict adherence to specific criteria. A systematic review follows explicit methodology to answer a well-defined research question by searching the literature comprehensively, evaluating the quantity and quality of research evidence rigorously, and analyzing the evidence to synthesize an answer to the research question. The evidence gathered in systematic reviews can be qualitative or quantitative. However, if adequate and comparable quantitative data are available then a meta-analysis can be performed to assess the weighted and summarized effect size of the studies included. Depending on the research question and the data collected, systematic reviews may or may not include quantitative meta-analyses; however, meta-analyses should be performed in the setting of a systematic review to ensure that all of the appropriate data were accessed. The components of a systematic review can be found in an important article by Moher et al. published in 2009 that defined requirements for systematic reviews and meta-analyses [ 2 ].

In order to optimize reporting of meta-analyses, an international group developed the Quality of Reporting of Meta-Analyses (QUOROM) statement at a meeting in 1996 that led to publication of the QUOROM statement in 1999 [ 3 ]. Moher et al. revised that document and re-named the guidelines the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). The PRISMA statement included both meta-analyses and systematic reviews, and the authors incorporated definitions established by the Cochrane Collaboration [ 4 ]. The PRISMA statement established the current standard for systematic reviews. To qualify as a systematic review, the methods section should acknowledge use of the PRISMA guidelines, and all PRISMA components should be incorporated strictly in all facets of the paper from the research question to the discussion. The PRISMA statement includes a checklist of 27 items that must be included when reporting a systematic review or meta-analysis [ 2 ]. A downloadable version of this checklist can be used by authors, reviewers, and journal editorial staff to ensure compliance with recommended components [ 5 ]. All 27 will not be listed in this brief editorial (although authors and reviewers are encouraged to consult the article by Moher et al. and familiarize themselves with all items), but a few will be highlighted.

The research question, as reflected in the title, should be a hypothesis-based specific research inquiry. The introduction must describe the rationale for the review and provide a specific goal or set of goals to be addressed. The type of systematic review, according to the Cochrane Collaboration, is based on the research question being asked and may assess diagnostic test accuracy, review prognostic studies evidence, evaluate intervention effect, scrutinize research methodology, or summarize qualitative evidence [ 6 ].

In the methods section, the participants, interventions, comparisons, outcomes and study design (PICOS) must be put forward. In addition to mentioning compliance with PRISMA, the methods section should state whether a review protocol exists and, if so, where it can be accessed (including a registration number). Systematic reviews are eligible for registration in the International Prospective Register of Systematic Reviews (PROSPERO) as established at the University of York (York, UK). When PROSPERO is used (it is available but not required for systematic reviews), registration should occur at the initial protocol stage of the review, and the final paper should direct to the information in the register. The methods section also must include specific study characteristics including databases used, years considered, languages of articles included, specific inclusion and exclusion criteria for studies; and rationale for each criterion must be included. Which individuals specifically performed searches should be noted. Electronic search strategy (with a full description of at least one electronic search strategy sufficient to allow replication of the search), process for article selection, data variables sought, assumptions and simplifications, methods for assessing bias risk of each individual study (such as selective reporting in individual studies) and utilization of this information in data synthesis, principal summary measures (risk ratio, hazard ratio, difference in means, etc.), methods of data management and combining study results, outcome level assessment, and other information should be reported.

The results section should include the number of studies identified, screened, evaluated for eligibility (including rationale for exclusion), and those included in the final synthesis. A PRISMA flow diagram should be included to provide this information succinctly [ 7 ]. The results also should include the study characteristics, study results, risk of bias within and across studies, and a qualitative or quantitative synthesis of the results of the included studies. This level of rigor in acquiring and evaluating the evidence of each individual study is one of the criteria that distinguishes systematic reviews from other categories. If the systematic review involves studies with paired samples and quantitative data, a summary of data should be provided for each intervention group along with effect estimates and confidence intervals for all outcomes of each study. If a meta-analysis is performed, then synthesized effect size should be reported with confidence intervals and measures of consistency (i.e. – data heterogeneity such as I 2 ) for each meta-analysis, and assessment of bias risk across studies. A forest plot, which provides a graphical presentation of the meta-analysis results, should be included.

The discussion section should summarize the main findings commenting on the strength of evidence for each outcome, as well as relevance to healthcare providers, policymakers and other key stake-holders; limitations of the study and outcomes; and conclusions highlighting the interpretation of results in the context of other research, and implications for future research.

Without adhering to of all of these criteria and the others listed in the PRISMA statement and checklist, the review does not qualify to be classified as “systematic”.

Meta-analyses

Meta-analyses, when feasible based on available and comparable quantitative data, supplement a systematic review evaluation, by adding a secondary statistical analysis of the pooled weighted outcomes of similar studies. This adds a level of objectivity in the synthesis of the review’s findings. Meta-analyses are appropriate when at least 2 individual studies contain paired samples (experimental group and control group) and provide quantitative outcome data and sample size. Studies that lack a control group may over-estimate the effect size of the experimental intervention or condition being studied and are not ideal for meta-analyses [ 8 ]. It also should be remembered that the conclusions of a meta-analysis are only as valid as the data on which the analysis is based. If the articles included are flawed, then the conclusions of the meta-analysis also may be flawed. Systematic reviews and meta-analyses are the most rigorous categories of review.

Other types of reviews

Mixed methods reviews.

Systematic reviews typically contain a single type of data, either qualitative or quantitative; however, mixed methods reviews bring together a combination of data types or study types. This approach may be utilized when quantitative data, in the setting of an intervention study, only provide a narrow perspective of the efficacy or effectiveness of the intervention. The addition of qualitative data or qualitative studies may provide a more complete picture of the knowledge, attitudes, and behaviors of clinicians, patients or researchers regarding that intervention. This type of review could involve collecting either the quantitative or the qualitative data using systematic review methodology, but often the qualitative data are gathered using a convenience sampling. Many qualitative studies provide useful insights into clinical management and/or implementation of research interventions; and incorporating them into a mixed methods review may provide valuable perspective on a wide range of literature. Mixed methods reviews are not necessarily systematic in nature; however, authors conducting mixed methods reviews should follow systematic review methodology, when possible.

Literature and narrative reviews

Literature reviews include peer-reviewed original research, systematic reviews, and meta-analyses, but also may include conference abstracts, books, graduate degree theses, and other non-peer reviewed publications. The methods used to identify and evaluate studies should be specified, but they are less rigorous and comprehensive than those required for systematic reviews. Literature reviews can evaluate a broad topic but do not specifically articulate a specific question, nor do they synthesize the results of included studies rigorously. Like mixed method reviews, they provide an overview of published information on the topic, although they may be less comprehensive than integrative reviews; and, unlike systematic reviews, they do not need to support evidence-based clinical or research practices, or highlight high-quality evidence for the reader. Narrative reviews are similar to literature reviews and evaluate the same scope of literature. The terms sometimes are used interchangeably, and author bias in article selection and data interpretation is a potential concern in literature and narrative reviews.

Umbrella reviews

An umbrella review integrates previously published, high-quality reviews such as systematic reviews and meta-analyses. Its purpose is to synthesize information in previously published systematic reviews and meta-analyses into one convenient paper.

Rapid review

A rapid review uses systematic review methodology to evaluate existing research. It provides a quick synthesis of evidence and is used most commonly to assist in emergent decision-making such as that required to determine whether COVID-19 vaccines should receive emergent approval.

Scoping, mapping, and systematized reviews

If literature has not been reviewed comprehensively in a specific subject that is varied and complex, a mapping review (also called scoping review) may be useful to organize initial understanding of the topic and its available literature. While mapping reviews may be helpful in crystallizing research findings and may be published, they are particularly useful in helping to determine whether a topic is amenable to systematic review, and to help organize and direct the approach of the systematic review or other reviews of the subject. Systematized reviews are used most commonly by students. The systematized review provides initial assessment of a topic that is potentially appropriate for a systematic review, but a systematized review does not meet the rigorous criteria of a systematic review and has substantially more limited value. Additional types of reviews exist including critical review, state-of-the-art review, and others.

Reviews can be invaluable; but they also can be misleading. Systematic reviews and meta-analyses provide readers with the greatest confidence that rigorous efforts have attempted to eliminate bias and ensure validity, but even they have limitations based upon the strengths and weaknesses of the literature that they have assessed (and the skill and objectivity with which the authors have executed the review). Risks of bias, incomplete information and misinformation increase as the rigor of review methodology decreases. While review articles may summarize research related to a topic for readers, non-systematic reviews lack the rigor to answer adequately hypothesis-driven research questions that can influence evidence-based practice. Journal authors, reviewers, editorial staff, and should be cognizant of the strengths and weaknesses of review methodology and should consider them carefully as they assess the value of published review articles, particularly as they determine whether the information presented should alter their patient care.

Authors’ contributions

The author(s) read and approved the final manuscript.

Declarations

The authors declare no competing interests.

This article is co-published in the following journals: Journal of Voice, Otology & Neurotology, Ear, Nose and Throat Journal, Journal of Laryngology and Otology, Operative Techniques in Otolaryngology – Head and Neck Surgery, Head & Neck, International Journal of Pediatric Otorhinolaryngology, Journal of Neurological Surgery Part B: Skull Base, Otolaryngology – Head and Neck Surgery, World Journal of Otorhinolaryngology – Head and Neck Surgery, The Laryngoscope, American Journal of Rhinology & Allergy, Annals of Otology, Rhinology & Laryngology, Clinical Otolaryngology, American Journal of Otolaryngology, Laryngoscope Investigative Otolaryngology.

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