A prospective longitudinal study of depression, cognitive decline, and physical impairments in patients with Parkinson's disease.

A consecutive series of 105 patients with Parkinson's disease were examined for the presence of affective disorders, cognitive deficits, and impairments in activities of daily living (ADLs); 92 received the same evaluation 12 months after the initial examination. On the basis of the initial psychiatric findings, patients were divided into major, minor, and non-depressed groups. Patients with major depression showed a significantly greater cognitive decline, deterioration in ADLs, and further advance through the Hoehn and Yahr stages than patients with either minor depression or no depression.