Prevalence of Parkinson's disease-induced psychosis in a large U.S. managed care population.

Using 10 years' enrollment history, patients with non-drug-induced Parkinson's disease were identified, and the prevalence of Parkinson's disease-induced psychosis (PDP) was estimated using three different claims algorithms based on an expert working group criteria. The estimated prevalence of PDP ranged from 4 to 45/1,000 Parkinson's disease patients. PDP patients were just as likely to be male as female and were significantly older than Parkinson's disease patients without PDP. PDP patients more commonly had evidence of dementia and use of atypical antipsychotics. PDP occurs in up to 45,000 Parkinson's disease patients in the United States but represents a unique neuropsychiatric finding with important treatment implications.