Methylphenidate in primary obsessive-compulsive disorder.

An acute methylphenidate challenge was performed on 13 patients with primary obsessive-compulsive disorder. There was no overall effect of methylphenidate on mood or obsessive-compulsive behavior. However, on various behavioral scales, four patients had an antiobsessive-compulsive response and one patient an antidepressant response to methylphenidate. The clinical and theoretical implications of these findings are discussed.