Helen Niemeyer1, Jochen Musch, Reinhard Pietrowsky. 1. Heinrich-Heine-University, Department of Experimental Psychology, Universitätsstraße 1, 40225 Düsseldorf, Germany. helen.niemeyer@hhu.de
Abstract
OBJECTIVE: Meta-analyses are prone to publication bias, the problem of selective publication of studies with positive results. It is unclear whether the efficacy of psychotherapeutic interventions for schizophrenia is overestimated due to this problem. This study aims at enhancing the validity of the results of meta-analyses by investigating the degree and impact of publication bias. METHOD: Begg and Mazumdar's adjusted rank correlation test, Egger's regression analysis and the trim and fill procedure were applied to all systematic reviews up to September 2010 that reported the necessary data to assess publication bias. RESULTS: We examined 22 data sets, reported in 10 meta-analyses, for indications of publication bias. Begg's test indicated significant bias in 2 (9.09%) of these data sets, while Egger's test found bias in 3 (13.64%) of the data sets. The correction by the trim and fill procedure changed the significance of an effect size only once (4.55%), and did so unexpectedly in favor of the treatment condition. Psychosocial family interventions, regarding the outcome measure "leaving study early" in the time period between 13 and 24 months, were shown to be efficacious. DISCUSSION: Overall, we found only moderate evidence for the presence of publication bias. With one notable exception, the pattern of efficacy of psychotherapy for schizophrenia was not changed in the data sets in which publication bias was found. Several efficacious therapies exist, and their efficacy does not seem to be the result of publication bias.
OBJECTIVE: Meta-analyses are prone to publication bias, the problem of selective publication of studies with positive results. It is unclear whether the efficacy of psychotherapeutic interventions for schizophrenia is overestimated due to this problem. This study aims at enhancing the validity of the results of meta-analyses by investigating the degree and impact of publication bias. METHOD: Begg and Mazumdar's adjusted rank correlation test, Egger's regression analysis and the trim and fill procedure were applied to all systematic reviews up to September 2010 that reported the necessary data to assess publication bias. RESULTS: We examined 22 data sets, reported in 10 meta-analyses, for indications of publication bias. Begg's test indicated significant bias in 2 (9.09%) of these data sets, while Egger's test found bias in 3 (13.64%) of the data sets. The correction by the trim and fill procedure changed the significance of an effect size only once (4.55%), and did so unexpectedly in favor of the treatment condition. Psychosocial family interventions, regarding the outcome measure "leaving study early" in the time period between 13 and 24 months, were shown to be efficacious. DISCUSSION: Overall, we found only moderate evidence for the presence of publication bias. With one notable exception, the pattern of efficacy of psychotherapy for schizophrenia was not changed in the data sets in which publication bias was found. Several efficacious therapies exist, and their efficacy does not seem to be the result of publication bias.