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Kleine-Levin Syndrome

Medically Reviewed by Dr. Shelby Harris


The KLS is a rare neurological and sleep disorder in the hypersomnia family that mainly affects teenage boys. Like other hypersomnias including narcolepsy, Kleine-Levin syndrome involves excessive daytime sleepiness.

What is Kleine-Levin Syndrome?

Hunger, fixation on sex, and sleeping in are normal among teenage boys. But when these behaviors are extreme, it may be the Kleine-Levin Syndrome (KLS), or what some have dubbed “the Sleeping Beauty syndrome.”

The KLS is a rare neurological and sleep disorder in the hypersomnia family that mainly affects teenage boys. Like other hypersomnias including narcolepsy, Kleine-Levin syndrome involves excessive daytime sleepiness.

Symptoms of Kleine-Levin syndrome include excessive daytime sleepiness and sleeping for long stretches (patients sometimes wake only to eat and use the bathroom), sometimes accompanied by increased appetite and hypersexuality, for a period (also known as an “episode”) lasting as short as 2 and as long as 31 days. During an episode, patients may also experience confusion, disorientation, and hallucinations.

Patients in the midst of an episode of KLS typically are unable to attend school, work or practice self-care. They are unable to communicate effectively and struggle to get out of bed. After an episode ends, patients with KLS frequently experience some initial insomnia.

How common is Kleine-Levin syndrome?

This condition is rare, affecting fewer than 200,000 patients in the U.S. The median age of onset is 15.  About 70 percent of those with the disorder are adolescent males.

On average, patients experience 7 to 19 episodes lasting 10 to 13 days each, and relapse every 3.5 months. In between episodes, symptoms disappear. Relapses can occur for up to a decade before the illness spontaneously resolves. The sudden onset of each episode can be accompanied or triggered by flu-like symptoms or infections (38.2%), head trauma (9%), alcohol consumption (5.4%), or sleep deprivation.

What causes Kleine-Levin Syndrome?

The cause of Kleine-Levin syndrome is unknown, although the disorder has a strong genetic component. This uncommon sleep disorder tends to run in families, especially of Jewish ancestry. About 15 percent of the Kleine-Levin syndrome patients are of Jewish origin and “the incidence reported in Israel is unproportionately high,” according to a paper in a Jewish medical journal.

“The most promising findings are the familial clustering and a potential Jewish founder effect, supporting a role for genetic susceptibility factors,” according to French researchers. In addition, many cases appear to be triggered by flu-like symptoms, injections, or head trauma.


Practitioners use a comprehensive medical history to make a diagnosis of KLS. Because brain imaging does not show any abnormalities in Kleine-Levin syndrome patients, the criteria for diagnosis are clinical, relying on patients’ and families’ descriptions of abnormal behavior. It can often be quite difficult to get a patient into a sleep center for a comprehensive sleep study mid-episode, so sleep physicians frequently rely upon medical history and a sleep study whenever it is possible.


This disorder generally appears in adolescence and subsides on its own. Over time, episodes diminish in frequency and severity, becoming less disruptive to the individual and family. On average, it takes 8-14 years for patients to “outgrow” Kleine-Levin syndrome, with longer duration in men, in patients with hypersexuality, and when onset is after age 20.

Some medications that promote wakefulness can help correct sleep abnormalities and excessive sleepiness present in Kleine-Levin syndrome. Amphetamines and lithium have been used successfully in some patients. Amphetamines helped decrease the oversleeping in 40% of patients. According to the same review in the journal Brain, “lithium had a higher reported response rate (41%) for stopping relapses when compared to medical abstention (19%).”

Outside of these attempts to mitigate the symptoms, patients and their families are usually told to inform themselves, connect with others experiencing the same syndrome, and wait the disease out.

Additional Kleine-Levin Resources