Abstract
Parkinson's disease (PD) has frequently been associated with depression. However, estimates of the incidence and severity of depression in this disease vary greatly. This is partially due to the fact that the investigations to date have suffered from methodological problems, including both the samples and instruments used in these studies. Samples have been heterogeneous, and PD patients have rarely been compared to other patient groups, especially groups with progressive disease. The instruments used to assess depression often contain somatic items that may serve to inflate depression in patient groups. This investigation attempted to correct these problems. A total of 148 cases in three groups (PD, medical and nonmedical) were evaluated with regard to depression on three indices (Beck, Beck without somatic items, Millon Behavioral Health Inventory). All groups were also interviewed with regard to past psychiatric history; patients' spouses completed a depression checklist as well. Personality organization was also evaluated. Results indicated that the incidence and degree of depression in the PD group was not greater than that in another progressively diseased group; they were more depressed than a nonmedical group. However, the PD group reported a greater incidence of depression prior to disease onset, suggesting that the etiology of depression is different in these groups. In addition, the incidence of depression was highest in patient groups on the instruments that contained somatic items. There were no differences in the personality organization of the three groups. It was proposed that subtypes of depression may exist in PD, and that future investigations should include appropriate control groups and instruments before any conclusions are drawn regarding the depression of PD.