A systematic review of the clinical correlates of delusions in Parkinson's disease.

Introduction: Research within Parkinson's disease (PD) psychosis has mostly focused on hallucinations due to their higher prevalence, limiting our understanding of the clinical correlates of delusions. This review aims to systematically review the content and clinical correlates of delusions in PD, including demographic, motor and non-motor symptoms and medication. Method: Following PRISMA Guidelines, a search on Ovid Medline, PsycINFO, Web of Science and Embase was performed to include English language studies evaluating delusions in PD. Data extraction included study and patient characteristics, clinical factors, outcome measures and cognitive correlates. Risk of bias was assessed for each study. Results: Seven studies were eligible. Persecutory delusions were most commonly reported; and one study focused solely on delusional misidentification. Delusional jealousy was associated with younger age and shorter disease duration, and a single study reported a higher prevalence in men. Delusions were associated with motor symptoms but less strongly than hallucinations, neither were delusions associated with cognitive deficits, apart from delusional misidentification, which was associated with deficits in verbal memory and language. A diagnosis of depression and the severity of anxiety symptoms predicted the presence and number of delusional types. Dopamine agonists were commonly prescribed, but there was no association with prescribed dose. Conclusion: The small number and heterogeneity of the included studies limited interpretation and generalizability of our findings and emphasize the need for further investigation of the intersection of age, sex and dopamine agonist use in delusional jealousy, neuropsychological correlates of delusional misidentification and affective and psychological correlates of delusions.