Severity and Comorbidity Predict Episode Duration and Recurrence of DSM-IV Major Depressive Disorder

BACKGROUND: Information on the naturalistic outcome of major depressive disorder (MDD) is important in developing rational clinical practices. The aim of this study was to determine the outcome of MDD in a modern secondary-level psychiatric setting and the influence of comorbidity plus psychosocial factors on the outcome of MDD. METHOD: The Vantaa Depression Study is a prospective, naturalistic cohort study of 269 secondary-level care psychiatric outpatients and inpatients diagnosed with a new episode of DSM-IV MDD. Patients were initially interviewed to determine the presence of MDD using the World Health Organization Schedule for Clinical Assessment in Neuropsychiatry and to assess Axis II diagnoses using the Structured Clinical Interview for DSM-III-R personality disorders between February 1, 1997, and May 31, 1998, and were interviewed again at 6 months and 18 months. The exact duration of the index episode and the timing of relapses/recurrences were examined using a life chart. RESULTS: The median length of time that patients met full criteria for a major depressive episode was 1.5 (95% CL = 1.3 to 1.7) months, and the median time to full remission was 8.1 (95% CL = 5.2 to 11.0) months after entry. During the follow-up, 38% of patients had a recurrence. Although numerous factors predict outcome of MDD to some extent, severity of depression and current comorbidity were the 2 most important predictors of longer episode duration and recurrence. CONCLUSION: The course of MDD in modern psychiatric settings remains unfavorable. Any estimates of duration of depressive episodes and rates of recurrence are likely to be dependent on the severity of depression and level of comorbidity. At least among a population of mostly outpatients with MDD in medium-term follow-up, severity of depression and comorbidity appear to be more useful predictors of recurrence than does the number of prior episodes. These factors should influence clinical decision-making regarding the need for maintenance therapy.