Is there a relationship between Parkinson's disease and obsessive-compulsive disorder?

Obsessive-compulsive (OC) symptoms and obsessive-compulsive disorder (OCD) have been reported in Parkinson's disease (PD). This is interpreted as an indirect evidence for the involvement of frontobasal ganglia circuitry in OCD. However, the evidence for relationship between the OC symptoms and PD is inconsistent. This study systematically assessed OC symptoms and OCD in non-demented idiopathic PD patients (n=69) and matched medically ill controls (n=69). The cases did not differ from controls with respect to OC symptoms, clinical and subclinical OCD, tics and other psychiatric diagnoses. There was no relationship between severity of PD and OC symptoms. The findings do not support relationship between OCD and PD. While the findings of this study do not in any way rule out the involvement of frontobasal ganglia circuitry in OCD, it is speculated that the involvement of different circuitry in the pathophysiology of OCD and PD explain the lack of association between PD and OCD.