Factors associated with depression in Parkinson's disease

Depression is common in Parkinson's disease (PD) and contributes significantly to a reduced quality of life in PD patients. The determinants of depression in PD are complex and poorly understood. We investigated the factors associated with depression in PD.

PD patients were recruited from Neurology clinics. A validated method was used to screen for a lifetime history of depression. 'Depressed' patients were identified by a score of >6 in the Geriatric Depression Scale (GDS-15) or by having had prescribed treatment for depression. 'Never depressed' patients were recognised by a score of <5 in the GDS-15 with no signs of a history of depression. A newly developed and validated questionnaire was used to collect other information.

Depression was identified in 66% of the 639 PD patients who met the inclusion criteria. Depression was associated with an increased severity of illness as evidenced by higher Unified PD Rating Scale scores and a higher Hoehn and Yahr stage. Other clinical factors associated with disease severity were also more frequently observed in depressed patients. Similar to findings in non-PD samples, depressed PD patients were more likely to have a lower education level, a history of smoking and to regularly use non-aspirin based NSAIDs or analgesics. Comorbidities such as anxiety, memory problems, hallucinations, sleep disturbances and postural hypotension were more common in depressed PD patients.

To avoid patient exhaustion of over-surveying, some factors within the psychological domain were not examined.

Our results provide a focus for future intervention strategies.