Chronic depression : Determinants and consequences of chronic major depression in the general population

The subject of this thesis is chronicity of major depressive disorder (MDD). The main aims of the study are to examine: 1. the duration of a major depressive episode (MDE) and the rate of a chronic duration of MDE in the general population, 2. the determinants of (chronic) duration of MDE, 3. the consequences of a longer duration of MDE on daily functioning. The studies in the thesis were part of a general population survey amongst adults (18-64 year): the Netherlands Mental Health Survey and Incidence Study (NEMESIS) with three waves in 1996 (T0), 1997 (T1) and 1999 (T2). The diagnoses of psychiatric disorders in NEMESIS were based on DSM-III-R. The instrument used to determine the diagnoses was the Composite International Diagnostic Interview (CIDI) Version 1.1 (computerised version). Various determinants of the course of mental disorders were assessed. In the first study 28.3% of those depressed at baseline were still (or again) depressed one year later. Younger age, severe depression, melancholic symptoms (anhedonia and early morning awakening), longer duration of previous episodes, external locus of control and multiple negative life events were found as important risk factors for a poor outcome. Of the depressed individuals, 45.3% received professional care and 42.6% of these individuals were treated with antidepressants. Respondents treated within different levels of care (no professional care, primary care only and specialised mental health care), were found to differ on clinical factors and role dysfunctioning, but not on socio-demographic variables. In the following study duration of MDE was assessed in a cohort of 250 respondents with newly developed episodes. Of the respondents, 50% (95% CI 44- 56%) recovered within 3 months; 63% (95% CI 57-69%) within six months; 76% (95% CI 70-82%) within 12 months and 80% (95% CI 74-86%) within 21 months. The risk of a chronic course was the same in treated and in untreated depressed subjects. Just as in clinical populations, illness-related factors were found as the strongest predictors of episode duration: i.e. severity of the index episode and a longer duration of previous episodes. The index episode being a recurrent episode enhanced the speed of recovery. Lack of social support was also associated with longer duration and (chronic) physical illness had a predictive value on the duration of later depressive episodes. Functional disability was not found to be associated with duration of MDE but with severity of depression and comorbid anxiety. After symptomatic recovery, functioning improved to premorbid level, irrespective of the length of MDE. Functioning in daily activities improved with longer duration of recovery but social functioning did not. In conclusion: the rate of chronicity and the determinants of persistence of depression in the general population were very similar to clinical populations. The results suggest that MDD is a heterogeneous condition with a variable outcome. The implications of the results are especially applicable in primary care