Duration of subsequent episodes and periods of recovery in recurrent major depression

Background: Little is known about the duration of subsequent depressive episodes and periods of recovery, and much is based on potentially biased retrospective data. We therefore prospectively assessed whether duration of depressive episodes and recoveries is correlated within subjects and across episodes, and whether duration of subsequent depressive episodes and recoveries increases or decreases over time.

Methods: From a sample of 267 depressed primary care patients enrolled in a RCT, we identified 279 depressive episodes and 455 recovery periods during a 3-year follow-up. We correlated durations of depressive episodes and of recovery within subjects, and compared within subjects the duration of first depressive episodes after index depression with second and third episodes, and similarly with recovery periods.

Results: No significant correlations were found between duration of depressive episodes or between recovery periods within subjects (Rs ranging from -0.17 to 0.08; all Ps >0.05). Median duration of first and second depressive episodes was 11 (IQR 6-19) and 9 weeks (IQR 5-14). Median duration of first and second recovery periods was 16.5 (IQR 7-31) and 17.5 weeks (IQR 9-32). No significant increase or decrease was observed in duration of consecutive depressive episodes, nor in recovery periods across episodes (all Ps >0.05).

Conclusions: In this prospective study, we found no correlation between duration of depressive episodes or between recovery periods within subjects. Moreover, we found no support for an increase or decrease in subsequent duration of depressive episodes or a decrease in recovery periods across episodes. These findings do not support the notion that experiencing multiple depressive episodes results in a growing vulnerability.