<unk> , also known as sleep insufficiency 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. Acute<unk>  is when an individual sleeps less than usual or does not sleep at all for a short period of time – usually lasting one to two days. Chronic<unk>  means when an individual routinely sleeps less than an optimal amount for ideal functioning. Chronic sleep deficiency is often confused with the term insomnia. Although both chronic sleep deficiency and insomnia share decreased quantity and/or quality of sleep as well as impaired function, their difference lies on the ability to fall asleep. Sleep deprived individuals are able to fall asleep rapidly when allowed but those suffering from insomnia have difficulty falling asleep. The average adult needs seven or more hours of sleep per night to maintain health. The amount of sleep needed can depend on sleep quality, age, pregnancy, and level of<unk> . Insufficient sleep has been linked to weight gain, high blood pressure, diabetes, depression, heart disease, and strokes.<unk>  can also lead to high anxiety, irritability, erratic behavior, poor cognitive functioning and performance, and psychotic episodes. A chronic sleep-restricted state adversely affects the brain and cognitive function. However, in a subset of cases,<unk>  can paradoxically lead to increased energy and alertness and enhanced mood; although its long-term consequences have never been evaluated,<unk>  has even been used as a treatment for depression. Few studies have compared the effects of acute total<unk>  and chronic partial sleep restriction. A complete absence of sleep over a long period is not frequent in humans (unless they suffer from fatal insomnia or specific issues caused by surgery); it appears that brief microsleeps cannot be avoided. Long-term total<unk>  has caused death in lab animals.
Sleep deprivation
Sleep hygiene
Shift work sleep disorder
Nicotine withdrawal
Narcolepsy
Central sleep apnea
Sleep apnea
Circadian rhythm sleep disorder