Sleep deprivation
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.
Lack of sleep may result in irritability, blurred vision, slurred speech, memory lapses, overall confusion, hallucinations, nausea, and eventually death.
William C. Dement, M.D., Ph.D., is a leading researcher on sleep and sleep deprivation and is by some considered to be the world's leading authority on these subjects.