by Scholten A


Idiopathic hypersomnia (IH) is a rare sleep disorder. It is marked by excessive daytime sleepiness. This happens even after a full night of sleep. It can lead to problems with school, work, and relationships. Treatment may help.


The exact cause of IH is not known. It may be due to:

  • Genes
  • An imbalance of brain chemicals
  • Problems with the body’s internal clock

Risk Factors

IH often starts in people who are 16 to 21 years of age. However, it can start at a later age. This condition is more common in those with family members who have it.


Symptoms may be:

  • Excessive daytime sleepiness that:
    • Happens after a full night of sleep
    • Is not due to medicines or other health conditions
  • Being sleepy even after naps
  • Sleeping longer than normal and still feeling tired
  • Problems waking up
  • Problems thinking or doing things after waking up


The doctor will ask about symptoms and past health. A physical exam will be done.

To make the diagnosis the doctor may need:

  • Actigraphy—wearing a small device to measure sleep rhythms
  • Multiple sleep latency test (MSLT)—to assess daytime sleepiness
  • Polysomnography—to study brain waves and how the body works during sleep
  • Record of sleep pattern kept by patient

Diagnosis is based on tests and ruling out other causes. It is also based on symptoms lasting 3 months or longer.


Sometimes IH improves on its own. More often, symptoms need to be managed. There is no set treatment for IH. The doctor may recommend medicine to reduce daytime sleepiness. The medicine may need to be adjusted, changed, or combined over time to improve its effect. Scheduling work or school for later in the day may also help some.

Behavioral therapy may also help to cope with challenges of chronic illness. It can teach ways to ease frustration and loss caused by illness.


There are no steps to prevent IH.


American Sleep Association 

The National Sleep Foundation  


Canadian Sleep and Circadian Network  

Canadian Sleep Society 


Central disorders of hypersomnolence. EBSCO DynaMed website. Available at: Accessed May 10, 2021.

Do I have excessive sleepiness? National Sleep Foundation website. Available at: Accessed May 10, 2021

Hypersomnia. Sleep Foundation website. Available at: Accessed May 10, 2021.

Idiopathic hypersomnia. National Center for Advancing Translational Sciences website. Available at: Accessed May 10, 2021.

Idiopathic hypersomnia. Sleep Health Foundation website. Available at: Accessed May 10, 2021.

Trotti, LM. Idiopathic hypersomnia. Sleep Med Clin. 2017;12(3):331-344.

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