A hypothesis on Cotard's syndrome as an evolution of obsessive-compulsive disorder.

Cotard's syndrome usually presents as combined symptoms occurring in a broad series of neurological, psychiatric, and medical disorders, being severe depression the most frequent. The syndrome is not classified as a distinct clinical entity in the nosological systems but appears solely as a clinical condition in case reports. Thus, the diagnosis of Cotard's syndrome mainly centres on the psychiatric interview and the ability of the clinician to recognise specific symptoms due to the absence of both clinical instruments and diagnostic criteria.