Disorders characterized by hypersomnolence during normal waking hours that may impair cognitive functioning. Subtypes include primary hypersomnia disorders (e.g., idiopathic hypersomnolence; narcolepsy; and kleine-levin syndrome) and secondary hypersomnia disorders where excessive somnolence can be attributed to a known cause (e.g., drug affect, mental disorders, and sleep apnea syndrome). (From J Neurol Sci 1998 Jan 8;153(2):192-202; Thorpy, Principles and Practice of Sleep Medicine, 2nd ed, p320). The disease is MONDO_0004617 (recurrent hypersomnia). Also known as: primary recurrent hypersomnia.