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Understanding and interpreting systematic reviews and meta-analyses. Part 1: rationale, search strategy, and describing results
  1. John Geddes, MD1,
  2. Nick Freemantle, MA2,
  3. David Streiner, PhD3,
  4. Shirley Reynolds, MSc4
  1. 1Editor, Evidence-Based Mental Health
  2. 2Medicines Evaluation Group, Centre for Health Economics, University of York, UK
  3. 3Editor, Evidence-Based Mental Health
  4. 4Editor, Evidence-Based Mental Health

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Reviews of primary studies are an important source of information for clinicians, and we include abstracts of good quality reviews in Evidence-Based Mental Health. This issue contains summaries of reviews of the effectiveness of psychotherapy (Wampold p 78), cognitive therapy in depression (Gloaguen p 76), family and couples therapy for drug abuse (Stanton p 81), chlorpromazine in schizophrenia (Thornley p 83), interventions for old age depression (McCusker p 77), support after post-partum depression (Ray p 89), relative mortality in schizophrenia (Brown p 91) and the association between apolipoprotein E and Alzheimer's disease (Farrer p 94). All of these reviews tried to access and review systematically all of the relevant articles in the field (systematic review) and included a quantitative summary of their results (meta-analysis). The clinical interpretation of a review article, or an abstract of a review article, requires the reader to have some conceptual understanding of how systematic reviews are conducted and the rationale behind the approach. We address these issues in this article and discuss two important stages of a review—setting a clear research question and identifying the primary studies. We will focus on systematic reviews of treatment studies although similar principles apply to reviews of different kinds of studies.

In part 2 (November issue), we will describe some of the statistical issues that need to be considered when interpreting the results of a systematic review that uses statistical techniques to combine data from different studies (meta-analysis).

The need for systematic reviews

One of the more important methodological “discoveries” of the past two decades was that many review articles of health interventions were methodologically inadequate.1 Although there had been significant advances in research design, such as the development of the randomised controlled trial, the review article still tended to be unsystematic and susceptible to many biases. The result was that it …

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