Remitted psychotic depression (MDDPsy) has heterogeneity of outcome. The study's aims were to identify subgroups of persons with remitted MDDPsy with distinct trajectories of depression severity during continuation treatment and to detect predictors of membership to the worsening trajectory.

One hundred and twenty-six persons aged 18–85 years participated in a 36-week randomized placebo-controlled trial (RCT) that examined the clinical effects of continuing olanzapine once an episode of MDDPsy had remitted with sertraline plus olanzapine. Latent class mixed modeling was used to identify subgroups of participants with distinct trajectories of depression severity during the RCT. Machine learning was used to predict membership to the trajectories based on participant pre-trajectory characteristics.

Seventy-one (56.3%) participants belonged to a subgroup with a stable trajectory of depression scores and 55 (43.7%) belonged to a subgroup with a worsening trajectory. A random forest model with high prediction accuracy (AUC of 0.812) found that the strongest predictors of membership to the worsening subgroup were residual depression symptoms at onset of remission, followed by anxiety score at RCT baseline and age of onset of the first lifetime depressive episode. In a logistic regression model that examined depression score at onset of remission as the only predictor variable, the AUC (0.778) was close to that of the machine learning model.

Residual depression at onset of remission has high accuracy in predicting membership to worsening outcome of remitted MDDPsy. Research is needed to determine how best to optimize the outcome of psychotic MDDPsy with residual symptoms.

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.

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).

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.

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.