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Knowledge syntheses: Systematic & Scoping Reviews, and other review types


According to Pawson et al. (2005), a realist review, or a realist synthesis, is a method for studying complex interventions in response to the perceived limitations of conventional systematic review methodology. It involves identification of Contexts, Mechanisms and Outcomes for individual programs to explain differences, intended or unintended, between them. Pawson et al. (2005) add that "traditional methods of review focus on measuring and reporting on programme effectiveness, often find that the evidence is mixed or conflicting, and provide little or no clue as to why the intervention worked or did not work when applied in different contexts or circumstances, deployed by different stakeholders, or used for different purposes" (p. 21).

When is a Realist Review methodology appropriate?

When to Use It: As stated by Wong (2019), realist reviews are used when needing to answer the question “what works, for whom, under what circumstances?” Rycroft-Malone et al. (2012) state that realist reviews are "particularly appropriate for unpacking the impact of complex interventions because it works on the premise that one needs to understand how interventions work in different contexts, and why" (p. 9). Wong (2019) confirms that realist reviews are steadily on the rise. 

Elements of a Realist Review

The following characteristics, strengths, and challenges of conducting realist reviews are derived from Rycroft-Malone et al. (2012) and Pawson et al. (2005).


Rycroft-Malone et al. (2012) describe that "a realist synthesis follows similar stages to a traditional systematic review, but with some notable differences" which include:

  • The focus of the synthesis is derived from a negotiation between stakeholders and reviewers and therefore the extent of stakeholder involvement throughout the process is high.

  • The search and appraisal of evidence is purposive and theoretically driven with the aim of refining theory.
  • Multiple types of information and evidence can be included.
  • The process is iterative.
  • The findings from the synthesis focus on explaining to the reader why (or not) the intervention works and in what ways, to enable informed choices about further use and/or research.

  • The innate theory-driven approach in conducting realist reviews allows for coherent sense-making of complex interventions. 

  • According to Pawson et al. (2005), realist reviews have "an exploratory rather than judgmental focus" (p. 21), adding that they "seek to unpack the mechanism of how complex programmes work (or why they fail) in particular contexts and settings" (p. 21).

  • According to Pawson et al. (2005)realist reviews have "the potential to maximize learning across policy, disciplinary and organizational boundaries", mainly due to the programme theory approach it takes (p. 32). 

  • Finding balance: According to Rycroft-Malone et al. (2012), "the challenge of developing a framework for a realist synthesis is in finding a level of abstraction that allows reviewers to stand back from the detail and variation in the evidence, but that is also specific enough to meet the purpose of the review" (p. 3).

  • Rycroft-Malone et al. (2012) state that conducting a realist review "is not an easy option. Realist review[s] demands much of the reviewer, including an ability to think flexibly and deal with complexity" (p. 9).

  • Pawson et al. (2005) also state that realist reviews can't be applied in a wide variety of contexts, explaining that "realist review[s] cannot be used as a formulaic, protocol-driven approach. Realist review[s] [are] more about principles that guide than rules that regularize" (p. 32).

  • Pawson et al. (2005) also add that realist reviews are "not standarizable or reproducible the same sense as a conventional Cochrane review" (p. 32) and that realist reviews often only lead to, at the most, tentative recommendations. As well, it is important to note that realist reviews require considerable skill to complete and to date have not been published as much as other review types. 

Methods & guidance

The following resource provides further support on conducting a realist review:


  • Marchal, B., Belle, S. V., & Westhorp, G. (2018, April 18). Realist Evaluation. Retrieved from

  • Westhorp, G. (2015, February 27). Realist impact evaluation: an introduction. Retrieved from

  • Wong, G., MacPhee, M., Merrett, K., Miller, K., Taylor, S., & Pawliuk, C. (2020, March 10). The Realist Review Process Workshop [Presentation]. doi:



Check out the supplementary resources page for additional information, including articles, on realist reviews.