Context: Relatives of patients with Parkinson disease (PD) have an increased risk of PD and other neurologic disorders; however, their risk of psychiatric disorders remains uncertain.
Objective: To study the risk of depressive disorders and anxiety disorders among first-degree relatives of patients with PD compared with first-degree relatives of controls.
Design, setting, and participants: In a population-based, historical cohort study, we included 1000 first-degree relatives of 162 patients with PD and 850 first-degree relatives of 147 controls. Both patients with PD and controls were representative of the population of Olmsted County, Minnesota.
Main outcome measures: Documentation of psychiatric disorders was obtained for each relative separately through a combination of telephone interviews with the relatives (or their proxies) and review of their medical records from a records-linkage system (family study method). Psychiatric disorders were defined using clinical criteria from the DSM-IV or routine diagnoses.
Results: We found an increased risk of several psychiatric disorders in first-degree relatives of patients with PD compared with first-degree relatives of controls (hazard ratio [HR], 1.54; 95% confidence interval [CI], 1.21-1.95; P <.001). In particular, we found an increased risk of depressive disorders (HR, 1.45; 95% CI, 1.11-1.89; P = .006) and anxiety disorders (HR, 1.55; 95% CI, 1.05-2.28; P = .03). The results were consistent in analyses that adjusted for type of interview, excluded relatives who developed parkinsonism, or excluded relatives who developed both a depressive disorder and an anxiety disorder.
Conclusion: These findings suggest that depressive disorders and anxiety disorders may share familial susceptibility factors with PD.