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Publication bias in meta-analyses of the efficacy of psychotherapeutic interventions for depression.

OBJECTIVE
The aim of this study was to assess whether systematic reviews investigating psychotherapeutic interventions for depression are affected by publication bias. Only homogeneous data sets were included, as heterogeneous data sets can distort statistical tests of publication bias.


METHOD
We applied Begg and Mazumdar's adjusted rank correlation test, Egger's regression analysis, and the trim and fill procedure to assess the presence and magnitude of publication bias in all homogeneous data sets of systematic reviews published up to September 2010.


RESULTS
Thirty-one data sets reported in 19 meta-analyses fulfilled our inclusion criteria. Significant bias was detected in 5 (16.13%; rank correlation test) and 6 (19.35%; Egger's regression analysis) of these data sets. Applying the trim and fill procedure to amend presumably missing studies rarely changed the assessment of the efficacy of therapeutic interventions, with 2 exceptions. In 1 data set psychotherapy was no longer found to be significantly more efficacious than pharmacotherapy in reducing dropout at posttreatment when publication bias was taken into account. In the 2nd data set, after correcting for publication bias, there was no longer evidence that depressed patients without comorbid personality disorder profited more from psychotherapy and pharmacotherapy than patients with comorbid personality disorder.


CONCLUSIONS
The results suggest that taken together, psychotherapy research for depression is only marginally affected by the selective reporting of positive outcomes. With 2 notable exceptions, correcting for publication bias did not change the evaluation of the efficacy of psychotherapeutic interventions.