The Time Course of Nonchronic Major Depressive Disorder: Uniformity Across Episodes and Samples

BACKGROUND Most natural history studies of affective disorders have emphasized the prediction of eventual recovery. Little is known of changes over time in the immediate probability of recovery. METHODS To identify regularities in the timing of recovery from nonbipolar major depressive disorders, we considered only episodes that began during follow-up to increase the accuracy with which onsets were timed and to limit the study sample to individuals who had a demonstrably episodic course. Five participating centers conducted baseline assessments and followed probands (N = 605) and nonclinical subjects (relatives, controls, and spouses, N = 826) up for 6 years. During that time, 359 probands had at least one prospectively observed episode, and 181 had two episodes; corresponding numbers for the nonclinical subjects were 216 and 78, respectively. Our analyses considered the distribution of episode lengths across ascertainment source (probands vs nonclinical subjects), center, and episode number (first vs second prospectively observed episode). RESULTS Distribution was remarkably uniform. Regardless of ascertainment source, center, or episode number, recovery occurred within 3 months in 40% of episodes, within 6 months in 60%, and within 1 year in 80%; 20% had more protracted courses. CONCLUSIONS Once triggered, the immediate likelihood of recovery changes over time in a predictable fashion. This has practical implications for the study of antidepressant efficacy and theoretical implications for factors involved in affective dysregulation.