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Psychol Med. 2010 Feb;40(2):211-23. doi: 10.1017/S0033291709006114. Epub 2009 Jun 3.

The effects of psychotherapy for adult depression are overestimated: a meta-analysis of study quality and effect size.

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  • 1Department of Clinical Psychology, VU University Amsterdam, Amsterdam, The Netherlands. p.cuijpers@psy.vu.nl

Abstract

BACKGROUND:

No meta-analytical study has examined whether the quality of the studies examining psychotherapy for adult depression is associated with the effect sizes found. This study assesses this association.

METHOD:

We used a database of 115 randomized controlled trials in which 178 psychotherapies for adult depression were compared to a control condition. Eight quality criteria were assessed by two independent coders: participants met diagnostic criteria for a depressive disorder, a treatment manual was used, the therapists were trained, treatment integrity was checked, intention-to-treat analyses were used, N >or= 50, randomization was conducted by an independent party, and assessors of outcome were blinded.

RESULTS:

Only 11 studies (16 comparisons) met the eight quality criteria. The standardized mean effect size found for the high-quality studies (d=0.22) was significantly smaller than in the other studies (d=0.74, p<0.001), even after restricting the sample to the subset of other studies that used the kind of care-as-usual or non-specific controls that tended to be used in the high-quality studies. Heterogeneity was zero in the group of high-quality studies. The numbers needed to be treated in the high-quality studies was 8, while it was 2 in the lower-quality studies.

CONCLUSIONS:

We found strong evidence that the effects of psychotherapy for adult depression have been overestimated in meta-analytical studies. Although the effects of psychotherapy are significant, they are much smaller than was assumed until now, even after controlling for the type of control condition used.

PMID:
19490745
[PubMed - indexed for MEDLINE]
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