Impact of psychiatric disorders on Parkinson's disease: A nationwide follow-up study from Sweden

Objectives: To analyze whether hospitalization for a psychiatric disorder predicts Parkinson's disease (PD) in men and women in different age groups after accounting for socioeconomic status and geographical region. Methods: Data from the MigMed database were used to identify all people in Sweden hospitalized for psychiatric disorder and PD during the study period (1987 to 2001). Standardized incidence ratios (SIRs) with 95% confidence intervals (CI) for PD were calculated among those with and without hospitalization for psychiatric disorder. Results: There were 1876 cases of PD among those with psychiatric disorder during the study period. The risk of developing PD was strongest among those under age 50; the SIR was 11.56 (95% CI 9.15-14.41). The risk was attenuated with increasing age in both men and women. There were similar risk patterns in all subtypes of psychiatric disorders in PD patients. The overall risk of PD among people with psychiatric disorders was higher for women than men. Conclusions: A psychiatric disorder is an appreciable risk factor for the development of PD, particularly in people under age 50. The association between PD and psychiatric disorders should be taken into account by clinicians and health care providers.