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 wellsystematized, thematic ideas such as paranoia or in fidelity. PD psychosis may be due to extrinsic (i.e., pharmacological treatment) and/or intrinsic (i.e., diseaserelated) 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 causes (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 and quetiapine are favored. Effective and well-studied treatments that improve PD psychosis without worsening motor function are still needed.