[Meta-analyses. A tool for maximizing therapy study evidence?].
Medical decisions have to rely on evidence-based medicine. However, evidence is not a clearly defined term. Several evidence criteria have been proposed, yet statistical meta-analyses are considered to be core criterion of empirical studies in that they combine single evidence from different studies into an encompassing conclusion. We argue however that meta-analyses have major limitations in this context. Five arguments are presented: (1) the nature of a study design affects the results and thus comprehensive meta-analyses covering studies with different designs are not informative; (2) combining different studies into a meta-analysis is methodologically not informative; (3) meta-analyses consider the variance between studies not as informative but as random noise; (4) the strategy to identify informative studies is a decisive determinant of meta-analyses; and (5) the value of conclusions from meta-analyses depends on the choice of statistics chosen as combined results from the various single studies. Instead, meta-analyses are useful tools for generating hypotheses in a posteriori analysis.
Klinik für Psychiatrie und Psychotherapie der Rheinischen Friedrich-Wilhelms-Universität, Sigmund-Freud-Strasse 25, 53105, Bonn. Wolfgang.Maier@ukb.uni-bonn.de
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D002986:Clinical Trials as Topic / Q000639:trends*; D020000:Decision Support Systems, Clinical / Q000639:trends*; D019317:Evidence-Based Medicine / Q000639:trends*; D005858:Germany; D015201:Meta-Analysis as Topic; D011600:Psychopharmacology / Q000639:trends*