Sleep deprivation

Sleep deprivation, also known as sleep insufficiency^[2] or sleeplessness, is the condition of not having adequate duration and/or quality of sleep to support decent alertness, performance, and health. It can be either chronic or acute and may vary widely in severity. All known animals sleep or exhibit some form of sleep behavior, and the importance of sleep is self-evident for humans, as nearly a third of a person's life is spent sleeping.^[2]

The average adult needs to sleep for 7 to 8 hours every 24 hours, and sleep deprivation can occur if they do not get enough sleep.^[3] Acute sleep deprivation is when a person sleeps less than usual or does not sleep at all for a short period of time, normally lasting one to two days, but tends to follow the sleepless pattern for longer with no outside factors in play. Chronic sleep deprivation is when a person routinely sleeps less than an optimal amount for optimal functioning. Chronic sleep deficiency is often confused with the term insomnia^{[citation needed]}. Although both chronic sleep deficiency and insomnia share decreased quantity and/or quality of sleep as well as impaired function, their difference lies in the ability to fall asleep. To date, most sleep deprivation studies have focused on acute sleep deprivation, suggesting that acute sleep deprivation can cause significant damage to cognitive and emotional functions and brain mechanisms.^[4]

Sleep-deprived people are able to fall asleep rapidly when allowed, but those with insomnia have difficulty falling asleep overall.^[5]

The amount of sleep needed can depend on sleep quality, age, pregnancy, and level of sleep deprivation. Insufficient sleep has been linked to weight gain, high blood pressure, diabetes, depression, heart disease, and strokes.^[6] Sleep deprivation can also lead to high anxiety, irritability, erratic behavior, poor cognitive functioning and performance, and psychotic episodes.^[7]

A chronic sleep-restricted state adversely affects the brain and cognitive function.^[8] However, in a subset of cases, sleep deprivation can paradoxically lead to increased energy and alertness; although its long-term consequences have never been evaluated, sleep deprivation has even been used as a treatment for depression.^[9][10]

Few studies have compared the effects of acute total sleep deprivation and chronic partial sleep restriction.^[8] A complete absence of sleep over a long period is not frequent in humans (unless they have fatal insomnia or specific issues caused by surgery); it appears that brief microsleeps cannot be avoided.^[11] Long-term total sleep deprivation has caused death in lab animals.^[12]