Understanding the Phenomenology and Impact of Psychosis in Parkinson Disease: William Ondo, MD

WATCH TIME: 4 minutes

"Longitudinal studies suggest that most patients with PD will, in fact, develop psychosis at some point. Now, the phenomenology of PD psychosis tends to be relatively homogeneous, which is interesting in a [condition] that's one of the most heterogeneous diseases that we know of.”

Prior research has shown that up to 60% of patients with Parkinson disease (PD) will experience persistent psychotic symptoms at some point during the course of the condition.¹ Management of PD psychosis can begin with assessing and addressing potential contributing factors, such as systemic illnesses, psychiatric comorbidities, or substance use. Psychotic symptoms in PD can include hallucinations and delusions, but patients may also experience milder phenomena such as a sense of presence, passage hallucinations, and illusions. These subtle symptoms can still negatively affect patients, as research has linked them to an increased depressive symptoms and reduced quality of life.

At the 4th Annual Advanced Therapeutics in Movement and Related Disorders (ATMRD) Congress, held by the PMD Alliance from June 27-30, 2025,William Ondo, MD, director of the Movement Disorders Clinic at Houston Methodist Hospital, and Fay Bembry, PMH-NP, family nurse practitioner at Team Health, explored challenges and provided a review of the clinical efficacy and safety of treatment options for PD psychosis. During the session, the movement disorders experts presented real-world evidence from 2 retrospective analyses that investigated the risk of all-cause mortality among patients with PD psychosis treated with atypical antipsychotics.²

Following the session at the Congress, Ondo, who also serves as a professor of neurology at Weill Cornell Medical School, sat down with NeurologyLive^® to outline the core components of PD psychosis, including visual hallucinations and delusions. He explained the typical progression from minor perceptual disturbances like illusions and a sense of presence to more structured hallucinations and fixed false beliefs. The clinical severity, he noted, may be closely linked to the patient’s level of insight. Ondo also emphasized that although hallucinations may appear benign, they often signal significant impact on quality of life and should prompt consideration of treatment.

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REFERENCES
1. Chen JJ. Treatment of psychotic symptoms in patients with Parkinson disease. Ment Health Clin. 2018;7(6):262-270. Published 2018 Mar 23. doi:10.9740/mhc.2017.11.262
2. Ondo W, Bembry F. The First-Line Prescription Treatment for Hallucinations and Delusions Associated With Parkinson's Disease Psychosis. Presented at: ATMRD; June 27-30, 2025; Washington, DC. Sponsored by Acadia Pharmaceuticals.