Risk factors for depression in Parkinson disease.

OBJECTIVE: To evaluate whether depression in Parkinson disease (PD) is more closely related to the underlying neuropathological process or to environmental and psychological factors by correlating depression in PD with various clinical and demographic variables.
DESIGN: Major depression, level of depressive symptoms as measured with the Montgomery-Aasberg Depression Rating Scale (MADRS), and clinical characteristics were investigated in a community-based cross-sectional study of carefully diagnosed patients with PD. Both bivariate and multivariate correlation analyses were performed to investigate correlations and predictive values of possible risk factors for major depression and MADRS score in PD.
SETTING: Depression among patients with PD derived from a prevalence study in the county of Rogaland, Norway. PATIENTS: Two hundred forty-five patients with PD.
RESULTS: Impaired cognitive function and the presence of a thought disorder were significant predictors of major depression. A Mini-Mental State Examination sum score below 24 and level 2 or higher on the thought disorder subscale of the Unified Parkinson Disease Rating Scale increased the probability of major depression by a factor of 6.6 and 3.5, respectively. Higher MADRS scores were also associated with lower Mini-Mental State Examination score and higher thought disorder score. In addition, MADRS scores also correlated with more impairment in activities of daily living, presence of motor fluctuations, more evidence of atypical parkinsonism, higher daily doses of levodopa, and younger age on the day on which prevalence was determined.
CONCLUSIONS: Most of the observations of this study favor the hypothesis that depression in PD is a primary consequence of brain dysfunction. Situational factors may, however, also contribute to mood changes in PD.