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.
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.
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.
These findings suggest that depressive disorders and anxiety disorders may share familial susceptibility factors with PD.