Reliability, validity, and clinical correlates of apathy in Parkinson's disease.

The authors examined a consecutive series of 50 patients for the presence of apathy, depression, anxiety, and neuropsychological deficits using a neuropsychological battery that included a recently designed apathy scale. This scale was found to be reliable and valid in the diagnosis of apathy in patients with PD. Of patients in the study, 12% showed apathy as their primary psychiatric problem, and 30% were both apathetic and depressed. Patients with apathy (with or without depression), showed significantly more deficits in both tasks of verbal memory and time-dependent tasks. Results suggest that apathy is a frequent finding in PD, is significantly associated with specific cognitive impairments, and may have a different mechanism than depression.