Associations of specific psychiatric disorders with isolated focal dystonia, and monogenic and idiopathic Parkinson's disease

Comorbidity of psychiatric disorders in patients with movement disorders is common. Often, psychiatric symptoms manifest before the onset of the movement disorder, thus not representing a mere reaction to its burden. How the disease mechanisms of psychiatric and movement disorders are related is still poorly understood. The aim of the present study was to compare prevalence rates of specific psychiatric disorders between different movement disorders including isolated focal dystonia (IFD, N = 91), monogenic Parkinson's disease (PD, N = 41), idiopathic PD (N = 45), and a sample from a Northern Germany general population (TACOS Study; N = 4075). Our results indicate an odds ratio (OR) of 2.6 [confidence interval (CI) 1.7-4.0] for general axis I disorders in IFD, an OR of 2.5 (CI 1.4-4.7) in monogenic PD, and an OR of 1.4 (CI 0.8-2.6) in idiopathic PD. More specifically, the monogenic PD group showed the highest ORs for affective disorders including depression (OR = 4.9), bipolar disorder (OR = 17.4), and hypomanic episodes (OR = 17.0), whereas IFD expressed the highest rates of anxiety disorders (OR = 3.3). Psychotic symptoms were only observed in the PD groups but not in IFD. Our findings underline the notion that psychiatric disorders are part of the phenotypic spectrum of movement disorders. Moreover, they suggest that IFD, monogenic PD, and idiopathic PD are associated with specific psychiatric disorders indicating disturbances in a different neural circuitry for sensorimotor control.