The Effects of Blinding on the Outcomes of Psychotherapy and Pharmacotherapy for Adult Depression: a Meta-Analysis

Abstract

BackgroundRandomized trials with antidepressants are often run under double blind placebo-controlled conditions, whereas those with psychotherapies are mostly unblinded. This can introduce bias in favor of psychotherapy when the treatments are directly compared. In this meta-analysis, we examine this potential source of bias.MethodsWe searched Pubmed, PsycInfo, Embase and the Cochrane database (1966 to January 2014) by combining terms indicative of psychological treatment and depression, and limited to randomized trials. We included 35 trials (with 3721 patients) in which psychotherapy and pharmacotherapy for adult depression were directly compared with each other. We calculated effect sizes for each study indicating the difference between psychotherapy and pharmacotherapy at post-test. Then, we examined the difference between studies with a placebo condition and those without in moderator analyses.ResultsWe did not find a significant difference between the studies with and those without a placebo condition. The studies in which a placebo condition was included indicated no significant difference between psychotherapy and pharmacotherapy (g = −0.07; NNT = 25). Studies in which no placebo condition was included (and patients and clinicians in both conditions were not blinded), resulted in a small, but significant difference between psychotherapy and pharmacotherapy in favor of pharmacotherapy (g = −0.13; NNT = 14).ConclusionsStudies comparing psychotherapy and pharmacotherapy in which both groups of patients (and therapists) are not blinded (no placebo condition is included) result in a very small, but significantly higher effect for pharmacotherapy.

The efficacy of psychotherapy, pharmacotherapy and their combination on functioning and quality of life in depression: a meta-analysis

“…On the other hand, assignment to a blinded condition controls for expectancy effects and induction of hope, thus suggesting eventual underestimation of the effects of medication compared to psychotherapy (Gaudiano & Herbert, 2005). Nonetheless, a recent meta-analysis by Cuijpers et al (2015) comparing pharmacological studies involving or missing double blind condition to psychotherapy did not find any difference in the effects of both groups.…”

Complementary and Alternative Medicine Use and Its Association with Emotional Status and Quality of Life in Patients with a Solid Tumor: A Cross-Sectional Study

“…When evaluating the efficacy of CAM use for cancer-related symptoms such as anxiety and depression a placebo effect should be considered in both cohort studies and well-designed comparative studies. 56 For example, if CAM use is shown to improve anxiety and depression in 50% of patients the benefits of a placebo treatment should be shown in less than 50% of patients. The placebo effect is not well understood but may have had a strong influence of the results of the current study.…”

Effects of Cognitive Behavior Therapy on Heart Rate Variability in Young Females with Constipation-predominant Irritable Bowel Syndrome: A Parallel-group Trial

“…First, IBS patients assigned to CBT may have had a placebo effect, which is particularly applicable to certain conditions for which symptoms are subjective and chronic, such as IBS. 52 Owing to the nature of the intervention, participants may have known they were assigned to the treatment group and expected positive results. To reduce treatment bias, a third-party researcher who was blinded to group assignments monitored symptoms and HRV.…”