Presence of individual (residual) symptoms during depressive episodes and periods of remission: a 3-year prospective study

Background: Residual depressive symptomatology constitutes a substantial risk for relapse in depression. Treatment until full remission is achieved is therefore implicated. However, there is a lack of knowledge about the prevalence of (1) residual symptoms in general and (2) the individual residual symptoms in particular.
Method: In a 3-year prospective study of 267 initially depressed primary care patients we established per week the presence/absence of the individual DSM-IV depressive symptoms during subsequent major depressive episodes (MDEs) and episodes of (partial) remission. This was accomplished by means of 12 assessments at 3-monthly intervals with the Composite International Diagnostic Interview (CIDI).
Results: In general, residual depressive symptomatology was substantial, with on average two symptoms present during remissions. Three individual symptoms (cognitive problems, lack of energy and sleeping problems) dominated the course of depression and were present 85-94% of the time during depressive episodes and 39-44% of the time during remissions.
Conclusions: Residual symptoms are prevalent, with some symptoms being present for almost half of the time during periods of remission. Treatment until full remission is achieved is not common practice, yet there is a clear need to do so to prevent relapse. Several treatment suggestions are made.