The goal of the proposed study is to evaluate the efficacy and safety of dronabinol in individuals with obsessive-compulsive disorder (OCD) or the obsessive-compulsive spectrum disorders, trichotillomania (TTM) or pathological skin picking (PSP). Fifteen patients with OCD, TTM, or PSP will receive 12 weeks of open-label treatment with dronabinol. The hypothesis to be tested is that dronabinol will be effective and well tolerated in patients with these disorders. The proposed study will provide needed data on the treatment of a disabling disorder that currently lacks a clearly effective treatment.