What Are Hypersomnias?

Reviewed by: HU Medical Review Board | Last reviewed: June 2020

The word hypersomnia comes from “hyper” meaning “too much” and “somnia” meaning “sleep.” These sleep disorders cause people to sleep an unusually long time during each 24 hour cycle, or fall asleep at inconvenient or dangerous times, such as while driving, eating, or talking. Hypersomnias are some of the rarest types of sleep disorders.1-2

What is hypersomnia?

People with hypersomnia do not sleep because they are tired but because they have a neurological condition. Their sleep does not re-energize them. Symptoms usually begin when the person is a teenager or young adult. People with these disorders may have trouble thinking clearly and be tired all the time.1-3

Treatments may include stimulants to keep the person awake during the day or while driving, antidepressants, exercise, and scheduled naps.2

What causes hypersomnia disorders?

Hypersomnia may be caused by a variety of conditions, including:2

  • A dysfunction of the nervous system
  • Drug or alcohol misuse or withdrawal
  • Brain injury caused by a tumor or an accident
  • Genetics

Some other health conditions that may be linked to hypersomnia include multiple sclerosis, Parkinson’s disease, depression, encephalitis, epilepsy, and obesity.2

Types of hypersomnias


Narcolepsy is the most well-known type of hypersomnia. It causes uncontrollable sleep attacks or severe sleepiness. These attacks may happen while the person is eating, working, driving, or walking. Some people also have cataplexy, which causes an inability to move or loss of muscle tone such as knees buckling. Cataplexy is triggered by strong emotions such as laughter or fear.4

Insufficient sleep syndrome

Insufficient sleep syndrome happens when someone regularly gets too little sleep. It is so common that most people may not realize regular sleep deprivation is considered a health condition. It is common to be tired and have problems staying alert, concentrating, or paying attention. Symptoms improve when the person gets enough sleep.5

Idiopathic hypersomnia

Idiopathic hypersomnia creates an irresistible urge to sleep during the day. People with this disorder may sleep 12-14 hours out of every 24 day. “Idiopathic” means “unknown cause.” It is rare.1,3

Kleine-Levin syndrome

Kleine-Levin syndrome is also called recurrent hypersomnia. This rare sleep disorder causes episodes that last from a few days to several weeks where the person sleeps for an average of 18 hours a day. Other symptoms include confusion, feelings of unreality, lack of motivation, compulsive eating, and hypersexuality. Symptoms come and go, with people going about their normal routines in between episodes.6

Long sleeper

Long sleeper describes people who need much more sleep than other people their age. Their sleep may be good quality, but because they need more than others, they may not get enough sleep.3

Research into hypersomnias

More than 200 studies were underway worldwide in 2020 to learn more about this rare group of sleep disorders. Doctors are looking at how new and existing drugs and other treatments may help people with hypersomnias, and how to better diagnose these conditions.7

Other types of sleep disorders include:

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