The epidemiology and differential diagnosis of obsessive compulsive disorder.

Obsessive compulsive disorder is now recognized as a common psychiatric disorder. The lifetime prevalence of 2% to 3% found in the United States has also been found in epidemiologic studies in several other countries with diverse cultures. This disorder has previously been underestimated due to a number of factors that include patients' reluctance to spontaneously admit to obsessions and compulsions and the omission of screening questions about obsessive compulsive disorder on routine mental status examinations. Depression and other anxiety disorders frequently co-occur with obsessive compulsive disorder, which may contribute to misdiagnosis. Patients with eating disorders, Gilles de la Tourette's syndrome, and schizophrenia have a greater comorbid risk compared with the general population. Differential diagnosis of obsessive compulsive disorder includes generalized anxiety disorder, panic disorder, phobias, compulsive personality disorder, and hypochondriasis. While many of these syndromes are characterized by intrusive thoughts, few have associated rituals. The complex tics seen in some patients with Tourette's syndrome may be difficult to distinguish from the compulsions seen in obsessive compulsive disorder, and, in fact, there is significant overlap in symptoms between the two disorders. Currently, the impulse control disorders, such as compulsive gambling and the paraphilias, are not considered to be part of obsessive compulsive disorder. Although the phenomenology of obsessive compulsive disorder appears to be quite diverse, with many distinct kinds of obsessions and compulsions, there are three important core features: abnormal risk assessment, pathologic doubt, and incompleteness. These features cut across phenomenological subtypes and may be useful in defining homogeneous subgroups with distinct treatment outcomes.