The spectrum of neuropsychiatric symptoms in patients with early untreated Parkinson's disease

Background: Neuropsychiatric symptoms are common in Parkinson's disease (PD) and have important clinical consequences for patients, caregivers and society. Few studies of neuropsychiatric symptoms in early untreated PD exist. Objective: To explore the range, clustering and correlates of neuropsychiatric symptoms in an incidence cohort of untreated subjects with PD. Methods: All cases with incident PD identified during a 22 month period in four counties of Western and Southern Norway were included. Standardised criteria were used to diagnose PD. The Neuropsychiatric Inventory (NPI) was administered to 175 PD and 166 healthy control subjects with similar age and sex distributions. Cluster analysis was used to investigate the interrelationship of NPI items. Results: The proportion with any NPI symptoms was higher in PD (56%) than in controls (22%) (p < 0.001). Depression (37%), apathy (27%), sleep disturbance (18%) and anxiety (17%) were the most common symptoms. Clinically significant symptoms occurred in 27% of the PD group compared with only 3% in the control group (p < .001). Subjects with clinically significant neuropsychiatric symptoms had more severe parkinsonism than those without. Two neuropsychiatric clusters were identified, one characterised by mood symptoms and one by apathy. Conclusions: Although the majority of patients with early untreated PD do not have clinical significant neuropsychiatric symptoms, these symptoms are more common in patients than in people without PD. Both psychological stress and brain changes associated with PD are likely to contribute to the higher frequencies.