Is Kleine-Levin syndrome a variant of bipolar disorder? An hypothesis

Kleine-Levin syndrome (KLS) was first described in 1862 by Brierre de Boismont and gained its eponymous name from the reports of Willi Kleine (1) and Max Levin (2) in the 1920s. It is a rare disorder that occurs worldwide and is characterised by episodes of sleep, behavioural, mood and cognitive disturbance, with usually an onset in adolescence and a variable episodic course. The focus on hypersomnia has resulted in its characterisation as a sleep disorder (3), with hypersomnia and megaphagia being considered to be the core symptoms (4). The disorder has therefore remained in the domains of sleep medicine and neurology, with relatively little attention from psychiatry. A recent comprehensive review of 186 cases published between 1962 and 2004 (5) brought together the features of this syndrome that suggest its complexity and variety. Some similarities with primary mood disorder are obvious, and this paper proposes that there is heuristic value in considering KLS as a variant of bipolar disorder (BD). This paper does not present new data to support this conceptualisation but examines the existing information from a new perspective in order to inform future research.