Duration of major and minor depressive episodes and associated risk indicators in a psychiatric epidemiological cohort study of the general population.

OBJECTIVE: Hardly any studies exist on the duration of major depressive disorder (MDD) and factors that explain variations in episode duration that lack biases. This limits clinical decision-making and leaves patients wondering when they will recover.

METHOD: Data were used from the Netherlands Mental Health Survey and Incidence Study-2, a psychiatric epidemiological cohort study among a nationally representative adult population. Respondents with a newly originated depressive episode were selected: 286 MDD and 107 minor depressive disorder (MinDD) cases. DSM-IV diagnoses were assessed with the Composite International Diagnostic Interview 3.0 and episode duration with the Life Chart Interview.

RESULTS: Among MDD cases, median episode duration was 6 months, mean duration was 10.7 months, and 12% had not recovered at 36 months. Longer duration was associated with comorbid dysthymia, anxiety disorder, psychotropic medication use (i.e. antidepressants or benzodiazepines prescribed by a mental health professional), mental health care use and suicidal behaviour. Better physical and mental functioning before depression onset predicted shorter duration. Among MinDD cases, shorter median duration (3 months) but similar mean duration (8.7 months), risk of chronicity (10% not recovered at 36 months) and risk indicators for episode duration were found.

CONCLUSION: As the risk of chronicity was similar for MDD and MinDD, MinDD cannot be dismissed as a merely brief mood state.