Psychosis not uncommon in Parkinson’s disease, signals cognitive decline

A significant presence of psychosis exists among patients with Parkinson’s disease (PD) in Singapore, potentially indicating a more rapid cognitive decline and progression of PD severity, reports a study.

“Knowing the negative implications of psychosis on the quality of life of patients with PD, it would be worthwhile for psychiatrists to collaborate with movement disorders specialists for constructing a standardized screening tool to specifically assess for PD-associated psychosis that is applicable to the local population,” the researchers said.

“Establishing a standardized approach and translating this into clinical guidelines could facilitate the early detection of PD-associated psychosis and its timely intervention, which would be beneficial in the long-term management of patients with PD,” they added.

A total of 336 patients with PD, who presented to the National Neuroscience Institute, Singapore, in 2006 and 2007 and attended follow-up visits through 2013 were included in the analysis.

The researchers examined data containing scores from clinician assessments of cognitive function, disease severity, and presence of psychotic symptoms. They also performed survival analysis, as well as logistic and linear regression analyses.

Sixty-three patients with PD were diagnosed with psychosis, indicating a prevalence of 18.8 percent for PD-related psychosis and an incidence of 40 per 1,000 person-years. Demographic variables (ie, age at diagnosis of PD, gender, ethnicity, and years of education) did not significantly correlate with the likelihood of developing psychosis in PD. [Singapore Med J 2021;doi:10.11622/smedj.2021182]

This contrasted the findings of previous studies, which reported age of onset and female gender as independent risk factors for developing psychosis in PD. [Mov Disord 2013;28:755-762; BMC Neurol 2013;13:145]

In regression analyses, the presence of psychotic symptoms was significantly predictive of greater cognitive decline and disease severity. This finding was consistent with that of existing literature. [BMC Neurol 2013;13:145; Mov Disord 2012;27:858-863; Neurology 2001;57:2078-2082; J Neural Transm (Vienna) 2004;111:1447-1453]

“While causality cannot be inferred, this highlights the possibility that psychosis is a risk factor for cognitive impairment as well as higher disease severity in PD, which consequently serves to guide and inform clinicians in their treatment of patients,” the researchers said.

“Increasing cognitive impairment and worsening severity of PD may signal a need for vigilance in observing psychotic symptoms and vice versa,” they added.

Previous studies have suggested the role played by dopaminergic medications in PD-associated psychosis, but the current study was unable to examine the presence and effect of dopamine agonists as a potential precipitating factor due to a lack of access to medical databases. [J Neurol Neurosurg Psychiatry 2013;84:883-887; J Neurol Neurosurg Psychiatry 2011;82:1219-1224]

“Psychosis is a prominent neuropsychiatric symptom of PD and is associated with negative outcomes, such as poorer quality of life and greater rate of functional impairment,” the researchers said. “Early identification of patients with PD at risk of developing psychosis facilitates appropriate management to improve outcomes.”