Major depressive disorder in Parkinson's disease: a register-based study

Objective: To investigate whether patients with Parkinson's disease (PD) were at an increased risk of developing major depression compared with patients having other medical illnesses with a comparable degree of disability. Method: Case register linkage study of Danish Psychiatric Central Register (DPCR)and Danish National Hospital Register (DNHR). Three study cohorts were identified: all patients with PD, osteoarthritis, and diabetes. The rate of discharge diagnosis of depression on re-admission was estimated using competing risks models in survival analyses. The rates for patients with PD were compared with those of patients with osteoarthritis, and diabetes. Results: The study sample identified 211 245 patients in the hospital registers with one of the index diagnoses. An increased incidence of developing depression was found for women and men throughout their lifetime when this incidence was compared with the control groups. Conclusion: The findings support the hypothesis that depression in patients with PD is a consequence of brain dysfunction.