Sleep deprivation is an overall lack of the necessary amount of sleep. A person can be deprived of sleep by their own body and mind, insomnia, or actively deprived by another individual. Sleep deprivation is sometimes used as an instrument of torture, but in recent years it has been shown to be an effective treatment of depression and other mental illnesses.

Lack of sleep may result in irritability, blurred vision, slurred speech, memory lapses, overall confusion, nausea and eventually death.

William C Dement, M.D., Ph.D., is the world's leading authority on sleep and sleep deprivation.