The three-year naturalistic course of major depressive disorder, dysthymic disorder and double depression.

BACKGROUND Recent studies support a distinction between acute and chronic forms of depression, which contrasts the single-disease hypothesis for depressive disorders. Insight into the (determinants of) the 3-year naturalistic course of major depressive disorder (MDD), dysthymic disorder (Dysth) and double depression (DD) may contribute to this debate. METHODS Data were derived from NEMESIS, an epidemiologic survey in the adult population of the Netherlands. 400 Respondents who met the Composite International Diagnostic Interview (CIDI) criteria of MDD and/or Dysth were selected. Cox proportional hazards analyses and Linear Mixed Models were conducted to examine 3-year course trajectories of MDD, Dysth and DD and determinants for course. RESULTS Adjusted analyses showed similar course trajectories for Dysth and DD, which were significantly worse than the course for MDD. Determinants of unfavorable course were neuroticism and poor functioning. LIMITATIONS Attrition was higher among persons with Dysth. However, since attrition is generally associated with poorer outcome, this would indicate that differences in course may even have been larger in reality. CONCLUSIONS Dysth and DD involve a similar course which is worse than the course of MDD only. These results do not support a distinction between Dysth and DD. Duration of symptoms and level of functioning may serve as two clinically relevant classifying dimensions within the broad category of depressive disorders.