Depression in Parkinson's disease

Depression is a common accompaniment of Parkinson's disease. Reported prevalences vary from 2.7% to 90% [1,2] but most surveys have suggested 40-50% levels [3-7]. Depression affects all aspects of the patient's activities of daily living. Four surveys, one worldwide, have concluded that depression, disability, postural instability, medication, age and cognitive impairment are the major factors having the greatest influence on quality of life in Parkinson's disease [8(. .)9,10(.),11]. A prospective longitudinal study found significantly greater decline in activities of daily living over a 1-year period in Parkinson's disease patients with major depression compared to those who had only minor mood changes or those without depression [12]. It has been suggested that depression in Parkinson's disease may be qualitatively different from primary major depression with less associated suicide, guilt, feeling of failure, and self-blame [4,7,13]. Its neurochemical basis, however, remains unknown; is depression associated with Parkinson's disease an endogenous phenomenon, reflecting the pathophysiological substrate of the disease, or is it simply an adaptive response to motor disability?