The Occurrence of Depression in Parkinson's Disease

OBJECTIVE: To investigate the frequency of major depression (MD) and the severity of depressive symptoms among patients with Parkinson's disease (PD). DESIGN: The PD population was derived from a community-based prevalence study. Total case ascertainment and a high diagnostic accuracy of PD were attempted through a detailed community study and the use of a new clinical diagnostic classification. Major depression was diagnosed according to the criteria in the Diagnostic and Statistical Manual of Mental Disorders, Revised Third Edition. The severity of depression in the prevalence population was scored with the Montgomery and Asberg Depression Rating Scale. The occurrence of depressive symptoms among patients with PD was compared with the occurrence among age-matched groups of patients with diabetes mellitus and of healthy elderly. In addition, the patients with PD and the control groups completed the Beck Depression Inventory. 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. Two age-matched control groups (each including 100 patients); one group included patients with diabetes mellitus and the other, healthy elderly. RESULTS: Of the 245 patients with PD, 7.7% met the criteria for MD. Based on their Montgomery and Asberg Depression Rating score, 5.1% of the patients were moderately to severely depressed whereas another 45.5% had mild depressive symptoms. Among the patients who scored 20 or more on the Mini-Mental State Examination, 3.6% had MD compared with 25.6% of the patients with a score below 20. The frequency of patients with a Beck Depression Inventory score of 18 or more was higher in the PD group (24.1%) than among patients with diabetes mellitus (11%) and the healthy elderly controls (4%). CONCLUSION: This study suggests that the prevalence of MD in PD is lower than previously assumed, but a substantial proportion of patients with PD have less severe depressive symptoms.