Background: Psychosis is among the most disabling complications of Parkinson's disease (PD). The chronicity of PD psychosis remains understudied and the relative importance of dopaminergic therapy versus the disease process itself in engendering psychosis remains unclear.
Objectives: To examine pharmacologic and motoric correlates of PD psychosis onset and remission in a longitudinally monitored PD cohort.
Methods: We analyzed data from 165 participants enrolled in a longitudinal PD study through the Morris K. Udall Parkinson's Disease Research Center of Excellence at Johns Hopkins University. Evaluations included formal psychiatric assessment and were conducted at two-year intervals. Regression with generalized estimated equations (GEE) was used to produce unadjusted and adjusted estimates for time-varying longitudinal associations between psychosis and putative risk factors.
Results: Sixty-two participants (37.6%) were diagnosed with psychosis during at least one evaluation. Of forty-nine participants with psychosis followed over multiple evaluations, 13 (26.5%) demonstrated remission despite significant Hoehn & Yahr stage increase (p=0.009); two of these cases later relapsed. Multivariable regression with GEE identified dementia diagnosis, akinesia-rigidity, anticholinergic usage, and levodopa-carbidopa dose to be significantly associated with psychosis, while disease duration was not. A sub-analysis of 30 incident psychosis cases suggested that dopamine agonist dose was lowered after psychosis onset with a compensatory increase in levodopa-carbidopa dosage.
Conclusions: Our findings suggest that in the context of standard therapy, PD-related psychotic disorder can remit at a frequency of approximately 27%. Additionally, akinetic-rigid motor impairment was more strongly associated with psychosis than disease duration, independent of cognitive impairment and medications.
Keywords: Hallucinations; Motor subtypes; Parkinson’s disease; Psychosis; Remission.