Kleine-Levin syndrome

including menstrual-related hypersomnia

Kleine-Levin syndrome (KLS) is a rare hypersomnia sleep disorder of the brain (neurologic disorder). Researchers don’t yet know the cause of KLS, but it affects the brain’s ability to control sleep, wakefulness, thinking, and behaviors. KLS causes repeated episodes (periods) of very long sleep (often 16 to 20 hours a day) and excessive daytime sleepiness (EDS). EDS is a strong daytime sleepiness or need to sleep during the day, even with enough sleep the night before. 

KLS episodes may last for days or weeks at a time. During episodes, people who have KLS have other symptoms, such as:

  • Slow thinking and speaking
  • Memory loss
  • No motivation for talking, eating, or seeing people (major apathy)
  • Being exhausted and unable to get out of bed
  • Feeling that things they’re seeing or experiencing aren’t real 

They may also eat much more than they normally do and do things they wouldn’t usually do. However, all these symptoms usually go away between episodes.

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What are the symptoms of KLS?

Common symptoms during episodes include:

  • EDS — Excessive daytime sleepiness
  • Very long sleep
    • Sleeping much longer than usual, up to 16 to 20 hours per day
    • Waking or getting up only to eat and go to the bathroom
    • Being able to be woken up (arousable) but irritable if kept from sleeping 
  • Severely altered cognition — 
    • Being slow to answer questions or speak 
    • Feeling confused about where you are in time and sometimes in space 
    • Having some or complete memory loss (amnesia)
  • Derealization — The ongoing feeling that:
    • Things around you aren’t real
    • You’re watching yourself from outside your body (this is rare in KLS and also called depersonalization)
  • Major apathy — 
    • The complete lack of motivation to do usually enjoyable things such as talking with other people, using your smartphone or social media, bathing, or caring about what’s going on around you
    • Having mostly negative emotions, and finding it hard to feel or express positive emotions 
  • Disinhibited behavior — Trouble controlling impulses, which can lead to behavior problems, such as aggressive outbursts, hyperphagia, or hypersexuality
    • Hyperphagia is extreme hunger that is hard to satisfy, which can lead to eating too much or too fast
    • Hypersexuality is intense, ongoing sexual thoughts, urges, or behaviors

You don’t need to have all of these symptoms to be diagnosed with KLS, but you’ll have at least some of them.

When do KLS symptoms happen?

Symptoms most often start in adolescence or young adulthood, between 12 and 20 years of age. They can start later, but this is rare. 

An episode of KLS (excessive daytime sleepiness, sleeping for long times, and other KLS symptoms) can last from 2 days to several weeks. Episodes usually happen every few months.

If you have KLS, you may have times when you can function (do daily activities such as work or school) well or well enough, and other times when you don’t function well at all. Even if you function well at times, your symptoms should be taken seriously.

What may bring on (trigger) KLS episodes?

Triggers for first episodes (and possibly later episodes) include:

  • Infections, such as
    • Flu-like illness
    • Upper airway (nose and throat) infection
    • Digestive system infection (gastroenteritis)
  • Drinking alcohol 
  • Not getting enough sleep (sleep deprivation)
  • Stress
  • Travel
  • Head trauma
  • Menstrual periods

How long does KLS last?

KLS usually lasts around 14 years. Episodes usually become less long, less severe, and less frequent over that time. 

KLS is more likely to last longer in people who:

  • Are male sex
  • Were younger than 12 years or older than 20 years when their symptoms started
  • Have hypersexuality during their episodes

How common is KLS?

KLS is rare. Researchers estimate that about 1 in 250,000 people have it. So far, only around 1,000 cases have been reported worldwide, meaning there are many people who aren’t yet diagnosed. Males are about 2 times more likely than females to have KLS.

What’s it like to have KLS?

KLS can greatly affect a person’s daily life. During KLS episodes, people can’t do their normal daily activities or care for themselves for days to months at a time. People usually sleep up to 16 to 20 hours per day, waking or getting up only to eat and go to the bathroom. They can be woken up, but get irritable if they’re kept from sleeping. People usually can’t predict when their episodes will happen.  

These episodes cause people to have problems with: 

  • School
  • Work
  • Maintaining romantic or other relationships
  • Fully engaging with their friends and loved ones

Stories from people living with KLS

While almost everyone with KLS has episodes of EDS, other symptoms vary by person and can affect each person differently. For stories from people living with KLS, visit the KLS Foundation’s videos archives.

How will doctors know if I have KLS?

There are no specific tests for KLS. Doctors diagnose KLS based on specific diagnostic criteria and ruling out other disorders that can cause similar symptoms. Doctors start the diagnosis process by asking about your symptoms and medical history. The next step should be a complete physical exam and medical tests to make sure you don’t have other conditions that could be causing similar symptoms, such as multiple sclerosis or a brain tumor, infection, or inflammation.

What is menstrual-related hypersomnia?

Menstrual-related hypersomnia is also called menstrual-related KLS. This is when people only have episodes just before or during their menstrual periods.

What can help my symptoms?

To help your symptoms, you can:

  • Avoid triggers, such as alcohol, sleep deprivation, and infections
  • Try treatment with oral birth control pills, if your menstrual period is your only trigger 

To learn more about other treatments, visit this KLS Foundation web page.

Learn more

Visit our web page for doctors: “Diagnosis, classification, symptoms, and causes of hypersomnias.”

Published Jan. 16, 2024 |
Revised Jan. 28, 2024
Approved by our medical advisory board