Obsessive-compulsive disorder (OCD) is a chronic and often severe psychiatric disease. It is characterized by recurrent, intrusive and distressing thoughts, images, or impulses (obsessions) and/or repetitive mental or overt acts (compulsions or neutralizing behaviors) performed to reduce or remove distress and anxiety caused by these obsessive thoughts and to prevent any perceived harmful consequences (American Psychiatric Association, 2000). This disorder has a lifetime prevalence of approximately 2–3 percent worldwide (Weissman et al., 1994) and often begins in adolescence or early adulthood, usually with a gradual onset (American Psychiatric Association, 2000).