What contributes to depression in Parkinson's disease?

Background. Depression is a common problem in patients with Parkinson's dis ease, but its mechanism is poorly understood. It is thought that neurochemi cal changes contribute to its occurrence, but it is unclear why some patien ts develop depression and others do not. Using a community-based sample of patients with Parkinson's disease, we investigated the contributions of imp airment, disability and handicap to depression in Parkinson's disease. Methods. Ninety-seven patients seen in a population-based study on the prev alence of Parkinson's disease completed the Beck Depression Inventory (BDI) . Clinical and historical information on symptoms and complications of Park inson's disease were obtained from the patients by a neurologist. In additi on, clinician and patient ratings of disability on the Schwab and England s cale were obtained and a quality of life questionnaire was completed. Results. Moderate to severe depression (BDI greater than or equal to 18) wa s reported by 19.6 % of the patients. Higher depression scores were associa ted with advancing disease severity, recent self-reported deterioration, hi gher akinesia scores, a mini-mental score of < 25 and occurrence of falls. Disability as rated by the neurologist accounted for 34 % of the variance o f depression scores. Self-reported impairment of cognitive function and the feeling of stigmatization accounted for > 50 % of the variance of depressi on scores. Conclusions. Depression in patients with Parkinson's disease is associated with advancing disease severity, recent disease deterioration and occurrenc e of falls. Regression analysis suggests that depression in Parkinson's dis ease is more strongly influenced by the patients' perceptions of handicap t han by actual disability. The treatment of depression should therefore be t argeted independently of treatment of the motor symptoms of Parkinson's dis ease, and consider the patients' own perception of their disease.