This is an updated version of the original Cochrane review, published in 2009, Issue 2.

Kleine-Levin syndrome (KLS) is a rare disorder that mainly affects adolescent men. It is characterised by recurrent episodes of hypersomnia, usually accompanied by hyperphagia, cognitive and mood disturbances, abnormal behaviour, such as hypersexuality, and signs of dysautonomia.

In 1990, the diagnostic criteria for Kleine-Levin syndrome were modified in the International Classification of Sleep Disorders, where KLS was defined as a syndrome comprised of recurring episodes of undue sleepiness lasting some days, which may or may not be associated with hyperphagia and abnormal behaviour. According to the International Classification of Sleepiness Disorders, 3rd version (ICSD-3), revised in 2014, the Kleine-Levin syndrome is a disorder characterized by recurrent episodes of hypersomnia that last from two days to four weeks, with at least annual recurrence, and hyperphagia (rapid consumption of a large amount of food), usually with onset in early adolescence in males but occasionally in later life and in women. A monosymptomatic form of the disorder with hypersomnia only can occur without binge eating or hypersexuality.

The cause of Kleine-Levin syndrome remains unknown, and several treatment strategies have been used. Some medications have been reported to provide benefit in the treatment of patients with KLS, but because of the rarity of the condition, no long-term follow-up therapies have yet been described.