Background. Population-based studies suggest substantial co-morbidity between physical illness and depression in late-life. However, a causal relationship has not been established. If a relationship exists, it is important to establish which aspects of poor health determine risk for depression, and which factors confer vulnerability or resilience in the face of poor health. We investigate the role of disablement, measured as impairment, disability and handicap.

Methods. A prospective population-based cohort study, comprising an index assessment and 1 year follow-up, of all residents aged 65 years or over, of an electoral ward in London, UK (N=889).

Results. The prevalence of SHORT-CARE pervasive depression was 17·7% at index assessment. The 1 year onset rate for pervasive depression was 12·0%, and the 1 year maintenance rate 63·2%. There was a high mortality rate among the depressed. Disablement, particularly handicap was the most important predictor of the onset of depression (population attributable fraction, 0·69). Lack of contact with friends was a direct risk factor but also modified the association between handicap and depression. Marriage was protective for men, but a risk factor for women. Maintenance of depression was predicted by low levels of social support and social participation, rather than by disablement.

Conclusions. It seems likely that disablement, specifically handicap, is the chief cause of onsets of depression in late-life. Genetic predisposition, early adversity and serious life events may play a less prominent role than in earlier life. Effective prevention of late-life depression requires attention at the structural level to the sources of handicap within communities.