The validity of atypical depression in DSM-IV.

Atypical depression has been included in the DSM-IV as an episode specifier of major depressive episodes and dysthymia. This report will review evidence for the clinical validity of atypical depression using operational criteria for the validation of clinical syndromes. English language articles between 1969 and March 1996 were found using a computerized and manual reference search and were selected according to the following criteria: (1) primary research, (2) definition of atypical depression, which includes depression and not anxiety alone, and (3) relevance of data for validation of atypical depression. Studies were evaluated on Kendall's six criteria for establishing clinical validity. There are supporting data for diagnostic validity of atypical depression in the criteria of clinical description and differential treatment response, with atypical depression having a superior response to monoamine oxidase (MAO) inhibitors compared to tricyclic antidepressants. There is still only limited support for the validity of atypical depression in the criteria of pathophysiology, points of rarity with other similar diagnoses, distinctive course and outcome, and genetics. Based on the current evidence, atypical depression is a useful diagnostic concept, particularly for predicting differential drug response, but further research is required to conclusively demonstrate its validity as a clinical syndrome.