Double depression: a distinctive subtype of unipolar depression.

Whether depression is a single disease that varies from mild to severe, with varying episode durations and difficult course patterns, or whether it is an umbrella diagnosis representing depressive subtypes with different psychological and biological characteristics has been debated by clinicians and researchers for many years. However, most scientists now agree that understanding the heterogeneous subtypes of depression allows for greater accuracy in describing and differentiating patients suffering from depression and, therefore, greater precision in describing the most efficacious treatment plan. This article will focus on the distinctions between unipolar major depression, double depression and dysthymia, and will review the history of the DSM classifications for these "subtypes" of major depressive disorder, clinicians and researchers continue to subclassify major depression and, particularly, for the purpose of testing the efficacy of new psychopharmocologic and psychosocial treatments. There continues to be a need for future research to more clearly establish the predictive value in terms of course, recovery, rates of relapse and treatment in regard to distinguishing type of depression as well as to validate the current nosology.