The new Caucus-race: Methodological considerations for meta-analyses of psychotherapy outcome.

The Dodo Bird Verdict (DBV)—the proposition that all psychotherapies are equally effective—remains bitterly contested by researchers, who have mainly used meta-analyses as the primary tool to adjudicate the disagreements about relative psychotherapy efficacy. However, the meta-analytic literature remains inconclusive and contradictory, due in part to heterogeneity in researchers’ methodological and statistical decisions. We undertake a review of a number of recent meta-analyses of psychotherapy outcomes to highlight key methodological issues in the DBV meta-analytic literature. Issues under consideration include the inclusion of direct versus indirect comparisons; the restriction of analyses to bona fide rather than intent-to-fail treatments; the outcomes to be included and distinguished in the analysis (e.g., primary and secondary outcomes, outcomes at termination and at follow-up, intent-to-treat and completer analyses); methods for effect size aggregation; the question of what constitutes a clinically significant effect size; search strategies for locating primary studies; statistical considerations; and possible moderators for use in metaregression analysis, including treatment class, disorder, allegiance, and methodological quality. We conclude with recommendations for ensuring that meta-analytic assessments of the DBV are both accurate and even-handed. (PsycINFO Database Record (c) 2018 APA, all rights reserved)