idiopathic hypersomnia

Last edited 04/2020 and last reviewed 04/2020

  • this is the term used for a state of more or less permanent daytime drowsiness (despite lengthy night-time sleep), difficulty in waking, and unrefreshing naps (of up to 3-4 hours), and which has no identifiable cause
  • idiopathic hypersomnia thought to be less common than narcolepsy
  • a poorly understood syndrome in which excessive daytime sleepiness occurs despite adequate time asleep and after exclusion of other causes of excessive sleepiness such as hypothalamic disorders
  • diagnosis
    • requires thorough assessment in a specialist centre, including use of polysomnography and assessment of sleep latency
  • in the absence of a clear understanding of the pathogenesis of idiopathic hypersomnia, treatment is based on stimulant medications used in narcolepsy
  • Pitolisant may in the future become a management option for some patients (2)


  1. Drug and Therapeutics Bulletin (2004); 42(7):52-6.
  2. Brown J, Makker KM. An approach to excessive daytime sleepiness in adults. BMJ 2020;368:m1047