What is Kleine Levin Syndrome (KLS)?

Medically Reviewed by Dan Brennan, MD on February 20, 2024
Written by Lilianna Hogan
2 min read

Kleine-Levin Syndrome (KLS) is a rare sleep disorder usually seen in teenage boys (with that demographic representing 70% of all people affected). It is most recognizable through repeat episodes of excessive sleep. In between episodes, you may be unaffected or asymptomatic. 

Kleine-Levin Syndrome symptoms are associated with a part of the brain called the hypothalamus. The hypothalamus is known to regulate sleep, sex drive, hunger, thirst, and appetite. 

Kleine-Levin Syndrome falls under the diagnostic category of hypersomnia. This category simply describes specific sleep disorders that trigger long periods of sleep. Due to the difficulty of diagnosis, Kleine-Levin can often be misdiagnosed as a psychiatric disorder. 

Kleine-Levin Syndrome symptoms become less intense over time. A person over age 50 rarely has symptoms of KLS. 

While the exact cause of KLS is unknown, there is emerging evidence to suggest that cold or flu symptoms often precede a Kleine-Levin Syndrome episode. 

Researchers also speculate that KLS could be caused by a head injury, infection, infectious disease, or autoimmune disorder. Rarely is more than one family member affected by Kleine-Levin syndrome.

While KLS episodes are most closely associated with large amounts of sleep, they can also bring about specific behavioral changes, increased hunger, and hypersexuality. Each episode can last a minimum of a week and a maximum of two months.  

People with KLS may go long periods without an episode, and not feel any of its effects. Most people have between two to 12 episodes every year. Typically, symptoms do not happen past age 40.

During episodes, you may:

  • Sleep for up to twenty hours at a time
  • Be irritable
  • Feel sleepy when awake
  • Feel indifferent toward others
  • Feel confusion
  • See hallucinations
  • Eat more than normal
  • Only wake up to eat, drink, and use the toilet
  • Feel detached from reality
  • Experience an abnormally high sex drive 
  • Misremember things
  • Be unable to concentrate
  • Feel depressed, anxious, or aggressive 

During episodes, you can become highly sleepy and disoriented. Episodes can happen spontaneously. Due to this, many people with Kleine-Levin Syndrome wear medical jewelry or carry other identifying items that describe Kleine-Levin Syndrome. 

It is challenging to diagnose Kleine-Levin Syndrome. Typically, other conditions with similar symptoms are first ruled out.  

KLS is often misdiagnosed as depression or bipolar disorder.

It may also be misinterpreted as:

  • Narcolepsy
  • Epilepsy
  • Multiple sclerosis
  • Tumors
  • Migraines
  • Side effects of benzodiazepines or illicit drugs

Conversations with your doctor will help them reach a diagnosis. They may also interview parents or others who have witnessed an episode to determine if you have KLS. 

Kleine-Levin Syndrome treatment aims at reducing symptoms, primarily through the use of medication.  

For sleepiness, doctors may prescribe stimulants such as:

Lithium is the most popular and effective drug for stabilizing someone experiencing a KLS episode and prolonging periods between episodes. Researchers speculate that the similarities between mood disorders and KLS could account for lithium’s ability to be effective in both situations. 

Other treatments are under study.