Specificity of CBT for Depression: A Contribution from Multiple Treatments Meta-analyses

The “Dodo bird verdict,” which claims that all psychotherapies are equally effective, has been a source of bewilderment and intense controversy among psychiatrists and psychologists. To examine this issue, we focused on cognitive-behavior therapy (CBT) and applied the newly developed review method known as multiple treatments meta-analysis (MTM). We identified randomized controlled trials comparing CBT against a psychological placebo (PP) and/or no treatment (NT) controls during the acute phase treatment of adults with depression. A random-effects MTM was conducted within a Bayesian framework. All the analyses were performed on an intention-to-treat basis. The MTM of the evidence network from 18 studies (39 treatment arms, 1,153 participants) revealed that CBT was significantly more likely to yield a response than NT (OR 2.24, 1.32–3.88) and that CBT was nominally, but not significantly, superior to PP (OR 1.30, 0.53–2.94), which in turn was superior to NT (OR 1.73, 0.67–4.84). The intervention effects in MTM were associated with the number of sessions, and the specificity of CBT increased as the number of sessions increased. The specific component of CBT was estimated to constitute 50.4 % (19.7–85.0) when CBT was given for ten or more sessions. Despite the quantitatively and qualitatively limited body of randomized evidence examining this issue, the present study strongly suggested a non-null specific component of CBT when given for an adequate length.