title: Sleep-laughing--hypnogely.
abstract: OBJECTIVE
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Sleep Research Unit, University Health Network, Toronto, Ontario, Canada. hypogely@gmail.com
authors.forename: Nikola N
authors.initials: NN
authors.lastname: Trajanovic
authors.forename: Colin M
authors.initials: CM
authors.lastname: Shapiro
authors.forename: Srdjan
authors.initials: S
authors.lastname: Milovanovic
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007845:Laughter; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D012893:Sleep Wake Disorders / Q000503:physiopathology*