Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by motor and nonmotor symptoms such as cognitive impairment and neuropsychiatric symptoms. The aim of this study was to investigate the spectrum of neuropsychiatric symptoms in PD according to cognitive function.

One hundred twenty seven patients with PD were consecutively recruited. They had undergone an intensive interview with a neurologist and the Seoul Neuropsychological Screening Battery-dementia version, and were divided into three groups: 27 patients in PD with normal cognition (PDNC), 57 in PD with mild cognitive impairment (PDMCI), and 43 in PD with Dementia (PDD). Forty five healthy controls without memory complaints were also recruited. The caregivers of all participants administered the Caregiver-Administered Neuropsychiatric Inventory (CGA-NPI).

There were significant differences in the CGA-NPI score (22.8±20.9 vs. 6.4±10.1 vs. 1.7±3.9 vs. 1.0±1.6, p <0.001), and the prevalence of neuropsychiatric symptoms (100% vs. 64.9% vs. 37.0% vs. 44.4%, p <0.001) among PDD, PDMCI, PDNC and control groups. Depression was the most common symptom (43.3%), followed by anxiety (31.5%), apathy (26.8%), and night-time behavior (26.8%) in all PD patients. Delusion, hallucination, and aberrant motor behavior were observed frequently in PDD, but were rare in PDMCI.

Depression was the most common neuropsychiatric symptom in PD. The presence of delusion, hallucination, or aberrant motor behavior may suggest PDD. The neuropsychiatric symptoms were not prevalent in PD with normal cognition.