Diagnosis of secondary depression in schizophrenia: implications for DSM-IV.

A substantial literature documents the existence of a secondary depression syndrome occurring in the course of schizophrenia. This review examines the relevance this syndrome may have in relation to demographic, symptomatic, biological, prognostic, and treatment issues. It explores the differential diagnosis of secondary depression in schizophrenia and considers the implications for the inclusion of such a diagnostic category DSM-IV.