How many well vs. unwell days can you expect over 10 years, once you become depressed?

Objective:  Prognostic studies of major depression have mainly focused on episode remission and relapse, and only a limited number of studies have examined long-term course of depressive symptomatology at threshold and subthreshold levels. Method:  The Group for Longitudinal Affective Disorders Study has conducted prospective serial assessments of a cohort of heretofore untreated major depressive episodes for 10 years under naturalistic conditions. Results:  Of the 94 patients in the cohort, the follow-up rate was 70% of the 11 280 person-months. Around 77% of the follow-up months were spent in euthymia, 16% in subthreshold depression and 7% in major depression. Duration of the index episode before reaching recovery was the only significant predictor of the ensuing well time. Conclusion:  On average, patients with major depression starting treatment today may expect to spend three quarters of the next decade in euthymia but the remaining one quarter in subthrehold or threshold depression.