Evidence for a biological hypothesis of obsessive-compulsive disorder

There is scant but provocative evidence to support the concept of a biological etiology in obsessive-compulsive disorder (OCD). This evidence includes the phenomenologic similarities and associations with other major psychiatric disorders for which there is evidence of biologic etiologies; the genetic studies that show an increased familial occurrence of psychiatric illness including OCD and concordance for this disorder in monozygotic twins; biologic evidence and the historical association of OCD and CNS damage; the treatment response of OCD to antidepressant medication and possibly those medications that selectively modify serotonin neuronal activity and to selective anterior limbic leukotomy. This evidence and the evidence linking OCD to depressive illness are specifically reviewed and discussed.