Differential response to placebo among patients with social phobia, panic disorder, and obsessive-compulsive disorder

Placebo effects in treatment of three anxiety disorders were compared.

Treatment response and patients' treatment expectancy were examined by using data from 70 patients with obsessive-compulsive disorder, social phobia, or panic disorder who received placebo in three randomized, controlled trials comparing cognitive behavior therapy, medication, and their combination to placebo.

Patients with obsessive-compulsive disorder were less likely to respond to placebo than patients with generalized social phobia or panic disorder. Differential expectancy did not account for these findings.

Further examination of the placebo effect across the anxiety disorders may elucidate maintenance mechanisms of these disorders and have implications for development of more effective treatments.