BACKGROUND: REM sleep behaviour disorder (RBD) is a known predictor of the subsequent development of neurodegenerative diseases, particularly Parkinson's disease and other alpha synucleinopathies. RBD has also been found to be common among children with other psychiatric disorders such as anxiety, depression, and ADHD. OBJECTIVE: This retrospective study aims to analyze the prevalence of early-onset psychiatric disorders among patients referred for RBD to our sleep laboratory. Our hypothesis is that early-onset psychiatric disorders are more common in patients with polysomnographically confirmed RBD. METHODS: A retrospective chart review was performed through the Kingston Health Sciences Centre (KHSC) Sleep Laboratory. Data collection involved gathering information regarding the patient's sleep study, psychiatric diagnoses and/or symptoms, mental health medication history and any neurodegenerative conditions noted in hospital clinical notes. RESULTS: Patients referred for and polysomnographically confirmed RBD were more likely to have presented with symptoms, or received a clinical diagnosis, of an early-onset psychiatric disorder at 32 % compared to the obstructive sleep apnea (OSA) control group at 3 %. CONCLUSIONS: History of early-onset psychiatric disorders is more common among patients referred as RBD compared to a control group of patients with OSA. Future studies are required to confirm the validity and replicability of this finding.