Absence of placebo response in obsessive-compulsive disorder

Analyses in 30 patients with a diagnosis of obsessive-compulsive disorder given single-blind placebo over a 2-week period and of 12 of these patients who continued treatment on double-blind placebo for an additional 10 weeks revealed virtual absence of improvement on both clinician and self-rating scales of obsessions, compulsions, phobias, depression, and anxiety. This result would imply that the contribution of the placebo effect to the pharmacotherapy of patients with obsessive-compulsive disorder is negligible although considerable effort and work is still required to reliably identify one of four panic disorder with agoraphobia patients who respond to placebo. The placebo response thus presents a clear distinction between these two phenomenologically complex anxiety disorders.