Classification of depressive disorders in the DSM-V: proposal for a two-dimension system.

The number of categories and specifiers for mood disorders has increased with each successive edition of the Diagnostic and Statistical Manual for Mental Disorders (DSM). Many of these categories and specifiers can be viewed as an effort to map the various permutations of severity and chronicity that characterize the depressive disorders. However, this has resulted in a system that (a) is unnecessarily complex and unwieldy, (b) has created problems with artificial distinctions between categories and artifactual comorbidity, and (c) at the same time obscures what may be more fundamental distinctions. A potentially useful and more parsimonious approach to capturing much of the heterogeneity of depressive disorders is to classify the depressive disorders along 2 dimensions, 1 reflecting severity and the other, chronicity. Considerations in the development of these dimensions are discussed, and a set of examples is presented. Although further research and discussion are needed to determine the optimal form of these dimensions, the next edition of the DSM should consider replacing many of the existing categories and specifiers for depressive disorders with the simpler approach of classifying depressive disorders using the 2 dimensions of severity and chronicity.