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Systematic Reviews & Evidence Synthesis Methods

A detailed, step-by-step guide to the first several stages of an evidence synthesis review.

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Types of Evidence Synthesis

Evidence synthesis refers to any method of identifying, selecting, and combining results from multiple studies. For help selecting a methodology, please refer to:


Types of evidence synthesis include: 

​​Systematic Review

  • Systematically and transparently collect and categorize existing evidence on a broad question of scientific, policy or management importance.
  • Compares, evaluates, and synthesizes evidence in a search for the effect of an intervention.
  • Time-intensive and often take months to a year or more to complete.
  • The most commonly referred to type of evidence synthesis. Sometimes confused as a blanket term for other types of reviews.

​​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 scientific, 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) or Peters et al (2020) 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.
  • Conducted as an additional step of a systematic review.

Video: Exploring different review methodologies (3:25 minutes)

Methodology Decision Tree

A decision tree asking questions about your research to determine what type of evidence synthesis review is most appropriate.

From Cornell University Library's Evidence Synthesis guide.