Kleine-Levin Syndrome (KLS) is characterized by recurring episodes of excessive sleepiness and periodic bouts of hypersomnia. During these periods, individuals often have stay in a dream-like state when awake and may display social withdrawal. Although the syndrome may resolve on its own, these periods can recur over several years and individuals may experience long-term effects on their sleep patterns and cognitive function.

What Is Kleine-Levin Syndrome?

Kleine-Levin Syndrome (KLS) is a type of recurrent hypersomnia. People with KLS experience episodes of excessive sleeping that last between a few days and a few weeks. They may need to sleep as many as 20 hours a day. These episodes of needing extra sleep can occur multiple times in a year but eventually subside over time.

The disorder affects one to two people per million and primarily adolescent boys. KLS shares characteristics similar to narcolepsy and can cause excessive sleepiness and hunger .

Symptoms of Kleine-Levin Syndrome

The onset of KLS is sudden and may at first present like the flu. The primary symptom is excessive sleepiness that requires you to sleep for extremely long periods of time, often more than 18 hours in a day . There are a number of additional changes in cognition and behavior that accompany the need to excessively sleep:

  • Increased Appetite: A common symptom of KLS is hyperphagia , or heightened focus on food and increased food intake. Typically, people with KLS eat any food offered to them   and especially crave sweet foods. They may increase their food intake to as many as six to eight meals a day .
  • Increased Sex Drive: People with KLS also commonly experience hypersexuality, although this symptom is more frequent in boys than girls. Hypersexuality may involve sexual comments, frequent masturbation, and undesired sexual advances.
  • Hallucinations: During episodes of KLS, people may experience derealization , or the dissociative feeling that they are detached from the world around them.
  • Irritability and Childishness: People experiencing KLS may be uncharacteristically irritable or aggressive, especially if they are denied food. They may also have verbal outbursts that are offensive, rude, or sexual in nature.
  • Anxious or Depressed Mood: People with KLS become withdrawn during episodes because they are unable to socialize as they normally do. About 15% of people with KLS report suicidal ideation.
  • Confusion and Amnesia: Some people with KLS may not recall all of their experiences during their KLS episodes.

These symptoms subside when the KLS episodes are over, and a person returns to their usual mood and demeanor. Some may experience continued memory loss.

Causes of Kleine-Levin Syndrome

The cause of KLS is currently unknown. Researchers have hypothesized multiple causes, including:

  • Infection
  • Physical trauma
  • Psychological disturbance
  • Toxins
  • Autoimmunity, in which the body attacks its own organs and tissue

Researchers also hypothesize that KLS is tied to the hypothalamus and thalamus, which are parts of the brain that regulate sleep, hunger, and sexual behavior.

Who Does Kleine-Levin Syndrome Affect the Most?

KLS is a sleep disorder that primarily affects teenagers. Boys are four times more likely to have the disorder than girls. Eighty-one percent of reported cases start in the second decade of life. People with KLS rarely experience their first episode after age 30.

Genetics may also play a factor. Around 5% of cases of KLS occur within families. Additionally, KLS is slightly more prevalent in the Ashkenazi Jewish population.

Risk Factors for Kleine-Levin Syndrome

A number of events associated with KLS have been documented. These include:

  • A cold or flu-like syndrome with a fever
  • Head trauma
  • Sleep deprivation
  • Extreme stress
  • Physical exertion
  • Traveling
  • Menses
  • Vaccination
  • Alcohol and marijuana use

Kleine-Levin Syndrome, Excessive Sleepiness, and Other Sleep Disorders

Often, KLS is first misdiagnosed as another type of sleep disorder, such as excessive sleepiness or narcolepsy. However, KLS differs from other sleep disorders. Patients with KLS do not experience sleep paralysis, cataplexy, or sleep-disordered breathing.

Because patients with KLS present with symptoms of depression or anxiety, they might also be initially diagnosed with a psychiatric illness. However, the depressive symptoms from KLS disappear once the episodes are over.

How Is Kleine-Levin Syndrome Diagnosed?

Typically, healthcare providers first rule out other disorders that have similar symptoms. Healthcare providers also verify that drugs or medications are not causing the symptoms.

To be diagnosed with KLS, a person must meet first the criteria for recurrent hypersomnia:

  • Episodes of excessive sleepiness lasting between two days and five weeks
  • Episodes occur at least once every 18 months and often more frequently
  • Normal behavior and cognition between episodes

Other causes for hypersomnia must be ruled out. Then, in addition to hypersomnia, a person has to experience a minimum of one of the following:

  • Excessive hunger and compulsive eating
  • Hypersexuality
  • Impaired cognition, such as confusion or hallucinations
  • Unusual behavior, such as irritability or aggression

Sleep studies can verify the amount of time spent sleeping. Sleep tests can also measure electrical activity in the brain. In cases of KLS, brain activity slows down as much as 70% during sleep. Brain scans typically present as normal. Some physicians may test memory, and patients with KLS usually perform poorly.

Treatment for Kleine-Levin Syndrome

Treatments for KLS are not consistently effective. Supportive care at home, especially from parents or guardians, can help ensure a safe environment during episodes of KLS. Medications are recommended only as a secondary treatment. Some medications can reduce certain symptoms rather than eliminate KLS.

Supportive Care

Patient support is crucial to overall wellbeing. Caregivers can:

  • Ensure a comfortable, safe environment where the person with KLS can be supervised
  • Delay or postpone school and other activities until the KLS episode is over
  • Prevent the patient from operating a vehicle or heavy machinery
  • Watch for symptoms of anxiety, depression, and suicidal behavior
  • Maintain consistent sleep routines between KLS episodes
  • Encourage the person with KLS to avoid alcohol and to avoid contact with people who are sick


Medications do not completely prevent future episodes of KLS. Limited research suggests that lithium can reduce the number of episodes, but cannot eliminate them.

Some drugs may improve some symptoms of KLS but negatively impact others. For example, amphetamines and modafinil can treat sleepiness but worsen irritability. Temporary use of antidepressants or mood-stabilizing drugs may alleviate psychiatric symptoms. Antidepressants prevented relapse in only one known case.

When Should You Talk to Your Doctor About Kleine-Levin Syndrome?

If you experience symptoms of KLS, report them to your healthcare provider as early as possible. After an episode, some patients may feel embarrassed about their behavior or actions and be reluctant to share their symptoms. However, a clear understanding of your symptoms can help your doctor confirm diagnosis and develop an appropriate treatment plan.

Over time, KLS episodes typically reduce in frequency and severity. Oftentimes the episodes will spontaneously resolve. Those who have not experienced a KLS episode after six years are considered cured.

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8 Sources

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  3. Arnulf, I., Groos, E., & Dodet, P. (2018). Kleine–Levin syndrome: A neuropsychiatric disorder. Revue Neurologique, 174(4), 216–227.

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