Objectives: To describe further the phenomenology of drug-induced psychosis (DIP) in patients with Parkinson disease (PD) and assess which items on two common psychosis rating instruments-the Brief Psychiatric Rating Scale (BPRS) and the Neuropsychiatric Inventory (NPI)-are the best measure of DIP by comparing them with the Clinical Global Impression Scale (CGIS).
Methods: Baseline data from two placebo-controlled, double-blind studies of olanzapine in PD patients with DIP were collected and analyzed.
Results: A total of 157 of 160 patients had hallucinations, with visual hallucinations being the most common (97% of subjects), followed by auditory (48%), tactile (23%), and olfactory (16%). Seventy-six percent of subjects experienced delusions, and all types of delusions occurred with relatively equal frequency. The CGIS correlated with suspiciousness, hallucinatory behavior, unusual thought content, and hostility on the BPRS; and delusions, hallucinations, agitation, aberrant motor behavior, and sleep on the NPI.
Conclusion: Nonvisual hallucinations and delusions may occur more frequently in DIP than previously thought. These symptoms, plus agitation and hostility, may ultimately be the best measure of DIP in patients with PD.