Depressive illness: diagnostic issues.

Mental health professionals have made significant advances in the understanding of depression, yet controversies continue about the classification of subtypes. After reviewing the history of approaches to the diagnosis of depression, the author summarizes current knowledge of the clinical course of the illness and the relevance of this knowledge to diagnosis. He concludes with a discussion of the renewed interest in depressive personality disorder and its relationship to the official nomenclature, as well as to related disorders.