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Systematic Reviews

What is a Systematic Review?

From the Cochrane Handbook for Systematic Reviews of Interventions:

"A systematic review attempts to collate all empirical evidence that fits pre-specified eligibility criteria in order to answer a specific research question. It uses explicit, systematic methods that are selected with a view to minimizing bias, thus providing more reliable findings from which conclusions can be drawn and decisions made (Antman 1992, Oxman 1993). The key characteristics of a systematic review are:

  • a clearly stated set of objectives with pre-defined eligibility criteria for studies;

  • an explicit, reproducible methodology;

  • a systematic search that attempts to identify all studies that would meet the eligibility criteria;

  • an assessment of the validity of the findings of the included studies, for example through the assessment of risk of bias; and

  • a systematic presentation, and synthesis, of the characteristics and findings of the included studies."

Higgins, Julian. Cochrane Handbook for Systematic Reviews of Interventions. Hoboken, NJ, USA: John Wiley & Sons, 2009. ProQuest ebrary.



Video (2017): An Introduction to Conducting Systematic Reviews (26:46 minutes)

Andrea Goldstein Shipper
Health Sciences and Human Services Library, University of Maryland

Other Types of Reviews

Literature (Narrative) Review

  • A broad term referring to reviews with a wide scope and non-standardized methodology. 
  • Search strategies, comprehensiveness, and time range covered will vary and do not follow an established protocol.

​Scoping Review or Evidence Map

  • Systematically and transparently collect and categorize existing evidence on a broad question of policy or management importance.
  • Seeks to identify research gaps and opportunities for evidence synthesis rather than searching for the effect of an intervention. 
  • May critically evaluate existing evidence, but does not attempt to synthesize the results in the way a systematic review would. (see EE Journal and CIFOR)
  • May take longer than a systematic review.
  • See Arksey and O'Malley (2005) for methodological guidance.

​Rapid Review

  • Applies Systematic Review methodology within a time-constrained setting.
  • Employs methodological "shortcuts" (limiting search terms for example) at the risk of introducing bias.
  • Useful for addressing issues needing quick decisions, such as developing policy recommendations.
  • See Evidence Summaries: The Evolution of a Rapid Review Approach

Umbrella Review

  • Reviews other systematic reviews on a topic. 
  • Often defines a broader question than is typical of a traditional systematic review.
  • Most useful when there are competing interventions to consider.


  • Statistical technique for combining the findings from disparate quantitative studies.
  • Uses statistical methods to objectively evaluate, synthesize, and summarize results.
  • May be conducted independently or as part of a systematic review.


Evidence Synthesis Software Tools


litsearchr: a term harvesting tool

This is a beta version for an app that serves as a graphical interface for the R package litsearchr (Grames et al. 2019). If you use the app to generate search terms, please cite the paper describing the method, not the app itself. The app does not do everything the R package can do. Namely, it only extracts potential keywords and does not include author-tagged keywords, it does not suggest single-word search terms (i.e. unigrams), and it does not scrape grey literature results. For those features and more customization in the included functions, please use the litsearchr R package.