Family study of chronic depression in a community sample of young adults.

OBJECTIVE: The validity of the distinctions between dysthymic disorder, chronic major depressive disorder, and episodic major depressive disorder was examined in a family study of a large community sample of young adults.

METHOD: First-degree relatives (N=2,615) of 30 probands with dysthymic disorder, 65 probands with chronic major depressive disorder, 313 probands with episodic major depressive disorder, and 392 probands with no history of mood disorder were assessed by using direct interviews and informant reports.

RESULTS: The rates of major depressive disorder were significantly greater among the relatives of probands with dysthymic disorder and chronic major depressive disorder than among the relatives of probands with episodic major depressive disorder, who in turn exhibited a higher rate of major depressive disorder than the relatives of probands with no history of mood disorder. The relatives of probands with dysthymic disorder had a significantly higher rate of dysthymic disorder than the relatives of probands with no history of mood disorder, and the relatives of probands with chronic major depressive disorder had a significantly higher rate of chronic major depressive disorder than the relatives of probands with no history of mood disorder. However, the relatives of the three groups of probands with depression did not differ on rates of dysthymic disorder and chronic major depressive disorder.

CONCLUSIONS: Chronic depression is distinguished from episodic depression by a more severe familial liability. This familial liability may contribute to the more pernicious course of chronic depression.