Background. Previous research has yielded conflicting evidence regarding the long-term cognitive outcome of depression. Some studies have found evidence for a higher incidence of subsequent cognitive impairment or dementia, while others have refuted this.

Method. Depression, neuropsychological performance, functional ability and clinical variables were assessed in a sample of patients who had been hospitalized for depression 25 years previously.

Results. Data were available on 71 depressed patients (10 of whom were deceased) and 50 surgical controls. No significant differences were found between depressed subjects and controls on any neuropsychological measure. Ten depressed patients but no controls were found to have dementia at follow-up (continuity corrected χ2=5·93, P<0·01). Presence of dementia was predicted by older age at baseline. Vascular dementia was the most common type.

Conclusions. We conclude that this study did not find evidence that early onset depression is a risk factor for Alzheimer's disease, but that for a small subgroup there appears to be a link with vascular dementia. Several plausible explanations for this link, such as lifestyle factors, require further investigation.