Current Understanding of Psychosis in Parkinson's Disease.

Psychosis in Parkinson's disease (PD) is one of the greatest determinants of nursing home placement and caregiver stress. Traditionally associated with medications with dopaminergic effect, it has now been linked to other medications and other stressors e.g. systemic illnesses. The development of hallucinations in a PD patient can herald the onset of dementia and usually predicts increased mortality risk. Medication reduction in PD psychosis usually reduces the symptoms; however, this comes at the cost of worsening motor function. If gradually decreasing the patient's medications does not resolve the psychosis, the treatment of choice is an atypical antipychotic. Though only clozapine has level A recommendation for this indication, other atypicals like quetiapine continue to get used for this purpose on account of the logistics involved with clozapine use. Cholinesterase inhibitors are also increasingly being used for PD psychosis on account of the association with dementia. The treatment of PD psychosis is an unmet need in PD management and search for suitable agents constitutes an active area of research in PD.