Trajanovic, Nikola N. (56008805500)Nikola N. (56008805500)TrajanovicShapiro, Colin M. (7102469663)Colin M. (7102469663)ShapiroMilovanovic, Srdjan (25621995600)Srdjan (25621995600)Milovanovic2025-06-122025-06-122013https://doi.org/10.1017/S0317167100014621https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879376983&doi=10.1017%2fS0317167100014621&partnerID=40&md5=72c1eacbfed43516bf6633ee41065905https://remedy.med.bg.ac.rs/handle/123456789/9062Objective: To explain relatively common phenomenon of laughing during sleep and help to better define criteria for differentiating between physiological and pathological sleep-laughing. Methods: Observational study of patients who underwent a sleep assessment in a referential tertiary health facility. Results: A total of ten patients exhibited sleep laughing, nine of whom had episodes associated with rapid eye movement (REM) sleep. Also, in one of the patients sleep-laughing was one of the symptoms of REM sleep Behaviour Disorder, and in another patient sleep-laughing was associated with NREM sleep arousal parasomnia. Conclusion: The collected data and review of literature suggests that hypnogely in majority of the cases presents as a benign physiological phenomenon related to dreaming and REM sleep. Typically, these dreams are odd, bizarre or even unfunny for a person when awake. Nevertheless, they bring a sense of mirth and a genuine behavioural response. In a minority of cases, sleep-laughing appears to be a symptom of neurological disorders affecting the central nervous system. In these patients the behavioural substrate differs when compared to physiological laughing, and the sense of mirth is usually absent.