Prevalence and correlates of dysthymia and major depression among patients with Alzheimer's disease.

Objective: The purpose of this study was to examine the prevalence, risk factors, and correlates of depression among patients with Alzheimer's disease.

Method: A consecutive series of 103 patients with probable Alzheimer's disease were examined with a structured psychiatric interview and were assessed for the presence of cognitive impairments, deficits in activities of daily living, social functioning, and anosognosia.

Results: Fifty-one percent of the patients had depression (28% had dysthymia and 23% major depression). Women had a significantly higher prevalence of both major depression and dysthymia than men. Depressed and nondepressed patients had a similar frequency of family and personal histories of depression, a similar frequency of personality disorders before the onset of depression, and no significant differences in cognitive deficits and impairment in activities of daily living. Dysthymia usually started after the onset of dementia and was significantly more prevalent in the early stages of dementia; patients with dysthymia had a significantly better awareness of intellectual deficits than patients with major or no depression. On the other hand, patients with major depression had an earlier onset of depression (half of them before the onset of dementia), and the prevalence of major depression was similar across the different stages of the illness.

Conclusions: This study demonstrates a high prevalence of dysthymia and major depression among patients with probable Alzheimer's disease. While dysthymia may be an emotional reaction to the progressive cognitive decline, major depression may be related to biological factors.