Psychosis and Parkinson’s Disease

The clinical spectrum of Parkinson’s disease (PD) psychosis ranges from mild illusions to formed hallucinations or even frank delusions. Hallucinations occur in about one-third of PD patients treated with chronic dopaminergic therapy and are most often visual. Delusions are less common but typically consist of well-systematized, thematic ideas such as paranoia or infidelity. PD psychosis may be due to extrinsic (i.e., pharmacological treatment) and/or intrinsic (i.e., disease-related) factors. Risk factors for the development of psychosis include older age; advanced disease; akinetic-rigid motor phenotype; concomitant cognitive impairment, depression, or sleep disturbances; and multiple medical problems. When psychosis in PD develops acutely, becomes troublesome or frightening, or poses a safety risk, medical attention is necessary. Medical management of acute psychosis typically includes the following: identifying and addressing specific precipitants (e.g., infection, medications), reducing or discontinuing medications for PD and other conditions that may aggravate psychosis, and introducing antipsychotic medications. Since antipsychotics with dopamine-blocking properties may worsen parkinsonism, medications with greater serotonergic properties such as clozapine, pimavanserin, and quetiapine are favored, with pimavanserin having FDA approval in the United States. Effective and well-studied treatments that improve PD psychosis without worsening motor function or posing serious risks are still needed.