Hypersomnia

Hypersomnia is a neurological disorder marked by excessive time spent sleeping or by excessive sleepiness. It can arise from many possible causes, including seasonal affective disorder, and it can cause distress and problems with everyday functioning. In the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders, hypersomnolence appears among the sleep-wake disorders and has several subtypes. It is described as a pathological lack of alertness during the waking hours, which sets it apart from fatigue, a normal physiological state; daytime sleepiness shows most often in situations that demand little interaction. Because it impairs attention, quality of life can suffer, especially for people in jobs that need sustained alertness such as health care. It is also distinguished from clinophilia, in which a person deliberately stays in bed.