Psychosis associated to Parkinson's disease in the early stages: relevance of cognitive decline and depression

Objective To evaluate the prevalence of psychosis associated with Parkinson's disease (PSY-PD) in its early stages, its incidence over a 24 month follow-up period and the association with motor and non-motor clinical features. Methods PRIAMO is a 2 year longitudinal observational study that has enrolled patients with parkinsonism in 55 Italian centres. A cohort of 495 patients with early disease stage PD (baseline Hoehn and Yahr score <= 2, disease's duration (median) 3.4 years) were followed for 2 years. PSY-PD was evaluated by means of a clinician rated questionnaire and defined as the presence of at least one of the following symptoms occurring for at least 1 month: illusions, hallucinations, jealousy ideas and persecutory ideas. Patients with and without PSY-PD were compared on several clinical variables, encompassing motor and non-motor features. Results The prevalence of PSY-PD at baseline was 3%; the incidences at 12 and 24 months were 5.2% and 7.7%, respectively. Longer disease duration and prescription of dopamine agonists at baseline were associated with the development of PSY-PD over the 24 month period. At this follow-up time, worse disease severity, decline in cognitive performances, presence of depressive symptoms and anxiety were more frequently observed in PSY-PD. Conclusions Psychotic type symptoms may occur in the early stages of PD although less frequently than in later stages. Beyond dopaminergic treatment, there are disease related factors, such as disease severity and the occurrence of cognitive and depressive symptoms, which may underlie the onset of psychotic type symptoms from the earliest stages.