Objective: A considerable number of studies has examined whether adding psychotherapy to pharmacotherapy results in stronger effects than pharmacotherapy alone. However, earlier meta-analyses in this field have included only a limited number of available studies and did not conduct extended subgroup analyses to examine possible sources of heterogeneity.
Data sources: We used a database derived from a comprehensive literature search in PubMed, PsycINFO, EMBASE, and the Cochrane Central Register of Controlled Trials for studies published from 1966 to January 2008 that examined the psychological treatment of depression. The abstracts of these studies were identified by combining terms indicative of psychological treatment and depression.
Study selection: We included randomized trials in which the effects of a pharmacologic treatment were compared to the effects of a combined pharmacologic and psychological treatment in adults with a depressive disorder.
Data extraction: For each of the studies, we calculated a standardized mean effect size indicating the difference between pharmacotherapy and the combined treatment at posttest. We also coded major characteristics of the population, the interventions, and the quality and design of the study.
Data synthesis: Twenty-five randomized trials, with a total of 2,036 patients, were included. A mean effect size of d = 0.31 (95% CI, 0.20 approximately 0.43) was found for the 25 included studies, indicating a small effect in favor of the combined treatment over pharmacotherapy alone. Studies aimed at patients with dysthymia resulted in significantly lower effect sizes compared to studies aimed at patients with major depression, a finding that suggests that the added value of psychotherapy is less in patients with dysthymia. The dropout rate was significantly lower in the combined treatment group compared to the pharmacotherapy only group (OR = 0.65; 95% CI, 0.50 approximately 0.83).
Conclusions: Psychotherapy seems to have an additional value compared to pharmacotherapy alone for depression.
Copyright 2009 Physicians Postgraduate Press, Inc.