Psychosis

Abstract

An important unmet need in the care of Parkinson’s disease (PD) is the prediction, prevention, and satisfactory treatment of PD-associated psychosis (PDP). Psychosis in PD is predominantly medication induced and all antiparkinsonian drugs in current use are capable of producing PDP. Dementia and depression are strong predictors of risk for the development of PDP. Hallucinations and delusions can occur at any time in the course of PD, but they are most commonly seen as a later complication in susceptible individuals. Visual hallucination is the most common feature of PDP, although other types of hallucination have also been reported. Delusions, particularly paranoid type, are less common but represent a more serious clinical problem. The mechanisms responsible for producing PDP are not fully elucidated but important advances have been made. Treatment should be approached in a stepwise manner. A triggering factor, such as infection, should be excluded first. Then careful tapering of antiparkinsonian medication, starting with adjunctive medication, should be undertaken. If increased motor disability prevents adequate dosage reduction, quetiapine is a reasonable first-choice antipsychotic agent followed by clozapine.