Hypersomnia describes sleep disorders in which people sleep too much—either for prolonged periods at night or during the day. Some people normally sleep longer than others—ten or more hours a day—but this does not necessarily indicate a disorder. Seasonal affective disorder (SAD), described in the previous chapter, is a type of hypersomnia, in which people sleep in late, among other symptoms. Other variations of hypersomnia are as follows:
• Recurrent Hypersomnia—This disorder, which includes Kleine-Levin Syndrome, lasts several weeks and can recur periodically. Some cases are marked by binge eating and hypersexuality; it usually occurs in adolescent males.
• Idiopathic Hypersomnia—This type of hypersomnia has symptoms that may be mistaken for narcolepsy, including excessive daytime sleepiness and sleep attacks—except it does not include cataplexy.
• Posttraumatic Hypersomnia—People who have had head injuries may develop this type of disorder, usually immediately after the traumatic incident. Other symptoms include headaches and concentration and memory problems.
