The epidemiology and differential diagnosis of obsessive compulsive disorder.

Originally considered a rare disorder, obsessive compulsive disorder (OCD) has been shown to be quite common with a 1% point prevalence in many cultures. Comorbidity with other psychiatric disorders is common, with a lifetime history of major depression present in two thirds of OCD patients. This disorder also coexists with a number of other Axis I disorders including panic disorder, social phobia, eating disorders, and Tourette's disorder. Data collected on phenomenological subtypes have shown that most OC patients have multiple obsessions and compulsions. Another model for subtyping OC symptoms categorizes core features that underlie obsessions and compulsions. These core features such as abnormal risk assessment or incompleteness may be useful in identifying homogeneous subgroups that have distinct treatment responses. The presence of compulsions is helpful in distinguishing this disorder from other anxiety disorders as well as depression. The differential diagnosis of OCD is presented.