There is little evidence that total sleep loss, even for several days, produces any permanent or severe physical or psychological damage in humans. Much of our knowledge of the effects of lack of sleep over longer periods comes from research on animals.

Psychological symptoms of sleep deprivation are typically cognitive impairments such as shorter attention span and impaired memory, as well as anxiety and even hallucinations.

Examples of physiological effects are aches and pains, fatigue, chronic headaches and impaired immune system functioning. Studies on rats have shown that chronic sleep deprivation can result in death.