Supplementary Material for: Neuropsychiatric Traits Associated with Refractory Impulse Control Disorder in Parkinson’s Disease

Introduction: Impulse control disorder (ICD) in Parkinson’s disease (PD) is a critical nonmotor symptom with personality or neuropsychiatric traits contributing to ICD. Objective: This study aimed to identify predictive traits for persistent or paradoxical aggravation of ICD after dopamine agonist substitution therapy for ICD in PD. Methods: We conducted a case-control study using a database of a multicenter intervention trial for ICD in PD. The poor-outcome group was defined by showing paradoxical increases in ICD behaviors after the substitution of dopamine agonists with levodopa. We analyzed the pre-intervention personality traits associated with the poor outcome and also evaluated the risk traits for refractory ICD using a receiver-operating characteristic (ROC) curve analysis. Results: The poor-outcome group showed higher levels of anger expression (p =0.007) and obsessive-compulsive traits (p =0.009) compared with the good-outcome group at the pre-intervention state. In the ROC curve analysis, the Obsessive-Compulsive Inventory showed the highest area under the curve with 80.0% sensitivity and 74.3% specificity in discriminating against the poor-outcome group. Conclusions: Our results suggest that assessment of obsessive compulsiveness may be useful for predicting the refractoriness of ICD behaviors in planning an interventional treatment for ICD in PD.