a1 Department of Clinical Psychology, VU University Amsterdam, The Netherlands
a2 EMGO Institute for Health and Care Research, The Netherlands
a3 Behavioral Health and Neurosciences Division, Portland Veterans Affairs Medical Center, Portland, OR, USA
a4 Departments of Psychiatry and Pharmacology, Oregon Health and Science University, Portland, OR, USA
a5 Department of Preventive Medicine, Northwestern University, Chicago, IL, USA
a6 Department of Psychology, Boston University, Boston, MA, USA
a7 Department of Behavioral Sciences and Learning, Swedish Institute for Disability Research, Linköping University, Sweden
a8 Department of Clinical Neuroscience, Psychiatry Section, Karolinska Institutet, Stockholm, Sweden
a9 Department of Clinical Psychology, Philipps-University of Marburg, Germany
a10 Health Psychology Section, Department of Health Sciences, University Medical Center, Groningen, University of Groningen, The Netherlands
Background The effects of antidepressants for treating depressive disorders have been overestimated because of selective publication of positive trials. Reanalyses that include unpublished trials have yielded reduced effect sizes. This in turn has led to claims that antidepressants have clinically insignificant advantages over placebo and that psychotherapy is therefore a better alternative. To test this, we conducted a meta-analysis of studies comparing psychotherapy with pill placebo.
Method Ten 10 studies comparing psychotherapies with pill placebo were identified. In total, 1240 patients were included in these studies. For each study, Hedges’ g was calculated. Characteristics of the studies were extracted for subgroup and meta-regression analyses.
Results The effect of psychotherapy compared to pill placebo at post-test was g = 0.25 [95% confidence interval (CI) 0.14–0.36, I 2 = 0%, 95% CI 0–58]. This effect size corresponds to a number needed to treat (NNT) of 7.14 (95% CI 5.00–12.82). The psychotherapy conditions scored 2.66 points lower on the Hamilton Depression Rating Scale (HAMD) than the placebo conditions, and 3.20 points lower on the Beck Depression Inventory (BDI). Some indications for publication bias were found (two missing studies). We found no significant differences between subgroups of the studies and in meta-regression analyses we found no significant association between baseline severity and effect size.
Conclusions Although there are differences between the role of placebo in psychotherapy and pharmacotherapy research, psychotherapy has an effect size that is comparable to that of antidepressant medications. Whether these effects should be deemed clinically relevant remains open to debate.
(Received July 11 2012)
(Revised February 01 2013)
(Accepted February 05 2013)
(Online publication April 03 2013)
c1 Address for correspondence: P. Cuijpers, Ph.D., Professor of Clinical Psychology, Department of Clinical Psychology, VU University Amsterdam, Van der Boechorststraat 1, 1081 BT Amsterdam, The Netherlands. (Email: [email protected])