<h4>Aims</h4>To investigate the risk factors for early-onset psychosis in Parkinson's disease (PD) in a cohort of patients from the Parkinson's Progression Markers Initiative.<h4>Methods</h4>Longitudinal data on motor and non-motor features, dopamine transporter (DAT) imaging, and cerebrospinal fluid (CSF) measurements were collected. This evidence concerns the gene SLC6A3 and psychotic disorder.