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Sleep deprivation, 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. 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. Sleep deprivation is common as it affects about one-third of the population. (2025). 9780128153734 ISBN 9780128153734
The National Sleep Foundation recommends that adults aim for 7–9 hours of sleep per night, while children and teenagers require even more. For healthy individuals with normal sleep, the appropriate sleep duration for school-aged children is between 9 and 11 hours. Acute sleep deprivation occurs when a person sleeps less than usual or does not sleep at all for a short period, typically lasting one to two days. However, if the sleepless pattern persists without external factors, it may lead to chronic sleep issues. Chronic sleep deprivation occurs when a person routinely sleeps less than the amount required for proper functioning. The amount of sleep needed can depend on sleep quality, age, pregnancy, and level of sleep deprivation. Sleep deprivation is linked to various adverse health outcomes, including cognitive impairments, mood disturbances, and increased risk for chronic conditions. A meta-analysis published in Sleep Medicine Reviews indicates that individuals who experience chronic sleep deprivation are at a higher risk for developing conditions such as obesity, diabetes, and cardiovascular diseases.
Insufficient sleep has been linked to weight gain, high blood pressure, diabetes, depression, heart disease, and strokes. Sleep deprivation 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, 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.
To date, most sleep deprivation studies have focused on acute sleep deprivation, suggesting that acute sleep deprivation can cause significant damage to cognitive, emotional, and physical functions and brain mechanisms. Few studies have compared the effects of acute total sleep deprivation and chronic partial sleep restriction. 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 cannot be avoided. Long-term total sleep deprivation has caused death in lab animals.
According to the latest research, lack of sleep may cause more harm than previously thought and may lead to the permanent loss of brain cells. The negative effects of sleep deprivation on alertness and cognitive performance suggest decreases in brain activity and function. These changes primarily occur in two regions: the thalamus, a structure involved in alertness and attention, and the prefrontal cortex, a region subserving alertness, attention, and higher-order cognitive processes. Interestingly, the effects of sleep deprivation appear to be constant across "night owls" and "early birds", or different sleep chronotypes, as revealed by fMRI and graph theory.
Such Histology studies cannot be performed on humans for ethical reasons, but long-term studies show that sleep quality is more associated with gray matter volume reduction than age, occurring in areas like the precuneus. Sleep is necessary to repair cellular damage caused by reactive oxygen species and DNA damage. During long-term sleep deprivation, cellular damage aggregates up to a tipping point that triggers cellular degeneration and apoptosis. REM sleep deprivation causes an increase in Norepinephrine (which incidentally causes the person sleep deprived to be stressed) due to the neurons in the locus coeruleus producing it not ceasing to do so, which causes an increase in the activity of the Na⁺/K⁺-ATPase pump, which itself activates the intrinsic pathway of apoptosis and prevents autophagy, which also induces the mitochondrial pathway of apoptosis.
Sleep outside of the REM phase may allow enzymes to repair brain cell damage caused by free radicals. High metabolic activity while awake damages the enzymes themselves, preventing efficient repair. This study observed the first evidence of brain damage in rats as a direct result of sleep deprivation.
Crucially, individuals' subjective evaluations of their fatigue often do not predict actual performance on the PVT. While totally sleep-deprived individuals are usually aware of the degree of their impairment, lapses from chronic (lesser) sleep deprivation can build up over time so that they are equal in number and severity to the lapses occurring from total (acute) sleep deprivation. Chronically sleep-deprived people, however, continue to rate themselves considerably less impaired than totally sleep-deprived participants. Since people usually evaluate their capability on tasks like driving subjectively, their evaluations may lead them to the false conclusion that they can perform tasks that require constant attention when their abilities are in fact impaired.
The fatigue of drivers of goods trucks and passenger vehicles has come to the attention of authorities in many countries, where specific laws have been introduced with the aim of reducing the risk of traffic accidents due to driver fatigue. Rules concerning minimum break lengths, maximum shift lengths, and minimum time between shifts are common in the driving regulations used in different countries and regions, such as the drivers' working hours regulations in the European Union and hours of service regulations in the United States. The American Academy of Sleep Medicine (AASM) reports that one in every five serious motor vehicle injuries are related to driver fatigue. The National Sleep Foundation identifies several warning signs that a driver is dangerously fatigued. These include rolling down the window, turning up the radio, having trouble keeping eyes open, head-nodding, drifting out of their lane, and daydreaming. At particular risk are lone drivers between midnight and 6:00 a.m.
Sleep deprivation can negatively impact overall performance and has led to major fatal accidents. Due largely to the February 2009 crash of Colgan Air Flight 3407, which killed 50 people and was partially attributed to pilot fatigue, the FAA reviewed its procedures to ensure that pilots are sufficiently rested. Air traffic controllers were under scrutiny when, in 2010, there were 10 incidents of controllers falling asleep while on shift. The common practice of turn-around shifts caused sleep deprivation and was a contributing factor to all air traffic control incidents. The FAA reviewed its practices for shift changes, and the findings showed that controllers were not well rested. A 2004 study also found medical residents with less than four hours of sleep a night made more than twice as many errors as the 11% of surveyed residents who slept for more than seven hours a night.
Astronauts have reported performance errors and decreased cognitive ability during periods of extended working hours and wakefulness, as well as sleep loss caused by circadian rhythm disruption and environmental factors.
Depression and sleep are in a bidirectional relationship. Poor sleep can lead to the development of depression, and depression can cause insomnia, hypersomnia, or obstructive sleep apnea. About 75% of adult patients with depression can present with insomnia. Sleep deprivation, whether total or not, can induce significant anxiety, and longer sleep deprivations tend to result in an increased level of anxiety.
Sleep deprivation has also shown some positive effects on mood and can be used to treat depression. Chronotype can affect how sleep deprivation influences mood. Those with morningness (advanced sleep period or "lark") preference become more depressed after sleep deprivation, while those with eveningness (delayed sleep period or "owl") preference show an improvement in mood.
Mood and mental states can affect sleep as well. Increased agitation and arousal from anxiety or stress can keep one more aroused, awake, and alert.
On average, the latency in healthy adults decreases by a few minutes after a night without sleep, and the latency from sleep onset to slow-wave sleep is halved. Sleep latency is generally measured with the multiple sleep latency test (MSLT). In contrast, the maintenance of wakefulness test (MWT) also uses sleep latency, but this time as a measure of the capacity of the participants to stay awake (when asked to) instead of falling asleep.
To describe the temporal course of the sleep-wake cycle, a two-process model of sleep regulation can be mentioned. This model proposes a homeostatic process (Process S) and a circadian process (Process C) that interact to define the time and intensity of sleep. Process S represents the drive for sleep, increasing during wakefulness and decreasing during sleep until a defined threshold level, while Process C is the oscillator responsible for these levels. When being sleep deprived, homeostatic pressure accumulates to the point that waking functions will be degraded even at the highest circadian drive for wakefulness.
An even lighter type of sleep has been seen in rats that have been kept awake for long periods of time. In a process known as local sleep, specific localized brain regions went into periods of short (~80 ms) but frequent (~40/min) NREM-like states. Despite the on-and-off periods where neurons shut off, the rats appeared to be awake, although they performed poorly at tests.
In a study that followed over 160,000 healthy, non-obese adults, the subjects who self-reported sleep duration less than six hours a day were at increased risk for developing multiple cardiometabolic risk factors. They presented with increased central obesity, elevated fasting glucose, hypertension, low high-density lipoprotein, hypertriglyceridemia, and metabolic syndrome. The presence or lack of insomnia symptoms did not modify the effects of sleep duration in this study.
The United Kingdom Biobank studied nearly 500,000 adults who had no cardiovascular disease, and the subjects who slept less than six hours a day were associated with a 20 percent increase in the risk of developing myocardial infarction (MI) over a seven-year follow-up period. Interestingly, a long sleep duration of more than nine hours a night was also a risk factor.
Sleep quality is directly related to immunity levels. The team, led by Professor Cohen of Carnegie Mellon University in the United States, found that even a slight disturbance of sleep may affect the body's response to the cold virus. Those with better sleep quality had significantly higher blood T and B lymphocytes than those with poor sleep quality. These two lymphocytes are the main body of immune function in the human body.
An adequate amount of sleep improves the effects of vaccines that utilize adaptive immunity. When vaccines expose the body to a weakened or deactivated antigen, the body initiates an immune response. The immune system learns to recognize that antigen and attacks it when exposed again in the future. Studies have found that people who don't sleep the night after getting a vaccine are less likely to develop a proper immune response to the vaccine and sometimes even require a second dose. People who are sleep deprived in general also do not provide their bodies with sufficient time for an adequate immunological memory to form and, thus, can fail to benefit from vaccination.
People who sleep less than six hours a night are more susceptible to infection and are more likely to catch a cold or flu. A lack of sleep can also prolong the recovery time of patients in the intensive care unit (ICU).
In rats, prolonged, complete sleep deprivation increased both food intake and energy expenditure, with a net effect of weight loss and ultimately death. This study hypothesizes that the moderate chronic sleep debt associated with habitual short sleep is associated with increased appetite and energy expenditure, with the equation tipped towards food intake rather than expenditure in societies where high-calorie food is freely available.
In 2005, a study of over 1400 participants showed that participants who habitually slept fewer hours were more likely to have associations with type 2 diabetes. However, because this study was merely correlational, the direction of cause and effect between little sleep and diabetes is uncertain. The authors point to an earlier study that showed that experimental rather than habitual restriction of sleep resulted in impaired glucose tolerance (IGT).
Sleep deprivation may cause symptoms similar to:
To mitigate the effects of these environmental influences, individuals can consider strategies, such as using soundproofing measures, installing blackout curtains, adjusting room temperatures, investing in comfortable bedding, and improving air quality with purifiers. By addressing these environmental factors, individuals can enhance their sleep hygiene and overall health.
Insomnia can be grouped into primary and secondary, or Comorbidity, insomnia.
Primary insomnia is a sleep disorder not attributable to a medical, psychiatric, or environmental cause. There are three main types of primary insomnia. These include psychophysiological, idiopathic insomnia, and sleep state misperception (paradoxical insomnia). Psychophysiological insomnia is anxiety-induced. Idiopathic insomnia generally begins in childhood and lasts for the rest of a person's life. It's suggested that idiopathic insomnia is a neurochemical problem in a part of the brain that controls the sleep-wake cycle, resulting in either under-active sleep signals or over-active wake signals. Sleep state misperception is diagnosed when people get enough sleep but inaccurately perceive that their sleep is insufficient.
Secondary insomnia, or comorbid insomnia, occurs concurrently with other medical, neurological, psychological, and psychiatric conditions. Causation is not necessarily implied.Biological Rhythms, Sleep and Hypnosis by Simon Green Causes can be from depression, anxiety, and personality disorders.
Central sleep apnea is caused by a failure of the central nervous system to signal the body to breathe during sleep. Treatments similar to obstructive sleep apnea may be used, as well as other treatments such as adaptive servo ventilation and certain medications. Some medications, such as opioids, may contribute to or cause central sleep apnea.
Caffeine consumption, usually in the form of coffee, is one of the most widely used stimulants in the world. While there are short-term performance benefits to caffeine consumption, overuse can lead to insomnia symptoms or worsen pre-existing insomnia. Consuming caffeine to stay awake at night may lead to sleeplessness, anxiety, frequent nighttime awakenings, and overall poorer sleep quality. The main metabolite of melatonin (6-sulfatoxymelatonin) gets reduced with consumption of caffeine in the day, which is one of the mechanisms by which sleep is interrupted.
In the study, 70.6% of students reported obtaining less than 8 hours of sleep, and up to 27% of students may be at risk for at least one sleep disorder. Sleep deprivation is common in first-year college students as they adjust to the stress and social activities of college life.
Estevan et al. studied the relationships between sleep and test performance. They found that students tend to sleep less than usual the night before an exam and that exam performance was positively correlated with sleep duration.
A study performed by the Department of Psychology at the National Chung Cheng University in Taiwan concluded that freshmen received the least amount of sleep during the week.
Studies of later start times in schools have consistently reported benefits to adolescent sleep, health, and learning using a wide variety of methodological approaches. In contrast, there are no studies showing that early start times have any positive impact on sleep, health, or learning. Data from international studies demonstrate that "synchronized" start times for adolescents are far later than the start times in the overwhelming majority of educational institutions. In 1997, University of Minnesota researchers compared students who started school at 7:15 a.m. with those who started at 8:40 a.m. They found that students who started at 8:40 got higher grades and more sleep on weekday nights than those who started earlier. One in four U.S. high school students admits to falling asleep in class at least once a week.
It is known that during human adolescence, and, therefore, sleep patterns typically undergo marked changes. Electroencephalogram (EEG) studies indicate a 50% reduction in deep (stage 4) sleep and a 75% reduction in the peak amplitude of delta waves during NREM sleep in adolescence. School schedules are often incompatible with a corresponding delay in sleep offset, leading to a less than optimal amount of sleep for the majority of adolescents.
The specific causal relationships between sleep loss and effects on psychiatric disorders have been most extensively studied in patients with mood disorders. Shifts into mania in bipolar patients are often preceded by periods of insomnia, and sleep deprivation has been shown to induce a manic state in about 30% of patients. Sleep deprivation may represent a final common pathway in the genesis of mania, and manic patients usually have a continuous reduced need for sleep.American Psychiatry Association (2025). 9780890425558, American Psychiatric Publishing. ISBN 9780890425558
The symptoms of sleep deprivation and those of schizophrenia are parallel, including those of positive and cognitive symptoms.
Several questions are critical in evaluating sleep duration and quality, as well as the cause of sleep deprivation. Sleep patterns (typical bed time or rise time on weekdays and weekends), shift work, and frequency of naps can reveal the direct cause of poor sleep, and quality of sleep should be discussed to rule out any diseases such as obstructive sleep apnea and restless leg syndrome.
Sleep quality can be assessed using the Pittsburgh Sleep Quality Index (PSQI), a self-report questionnaire designed to measure sleep quality and disturbances over a one-month period.
Sleep hygiene recommendations include
CBT-i contains five different components:
As this approach has minimal adverse effects and long-term benefits, it is often preferred to (chronic) drug therapy.
Other strategies recommended by the American Academy of Sleep Medicine include
However, the American Academy of Sleep Medicine has said that the only sure and safe way to combat sleep deprivation is to increase nightly sleep time.
The incidence of relapse can be decreased by combining sleep deprivation with medication or a combination of light therapy and phase advance (going to bed substantially earlier than one's normal time). Many tricyclic antidepressants suppress REM sleep, providing additional evidence for a link between mood and sleep. Similarly, tranylcypromine has been shown to completely suppress REM sleep at adequate doses.
Sleep deprivation has been used as a treatment for depression.
In addition to the cognitive behavioral treatment of insomnia, there are also generally four approaches to treating insomnia medically. These are through the use of barbiturates, , and benzodiazepine receptor agonists. Barbiturates are not considered to be a primary source of treatment due to the fact that they have a low therapeutic index, while melatonin agonists are shown to have a higher therapeutic index.
Sleep deprivation has been used by the military in training programs to prepare personnel for combat experiences when proper sleep schedules are not realistic. Sleep deprivation is used to create a different schedule pattern that is beyond a typical 24-hour day. Sleep deprivation is pivotal in training games such as "Keep in Memory" exercises, where personnel practice memorizing everything they can while under intense stress physically and mentally and being able to describe in as much detail as they can remember of what they remember seeing days later. Sleep deprivation is used in training to create soldiers who are used to only going off of a few hours or minutes of sleep randomly when available.
DARPA initiated sleep research to create a highly resilient soldier capable of sustaining extremely prolonged wakefulness, inspired by the white-crowned sparrow's week-long sleeplessness during migration, at a time when it was not understood that migration birds actually slept with half of their brain. This pursuit aimed both to produce a "super soldier" able "to go for a minimum of seven days without sleep, and in the longer term perhaps at least double that time frame, while preserving high levels of mental and physical performance", and to enhance productivity in sleep-deprived personnel. Military experiments on sleep have been conducted on combatants and prisoners, such as those in Guantánamo, where controlled lighting is combined with torture techniques to manipulate sensory experiences. Crary highlights how constant illumination and the removal of day-night distinctions create what he defines as a "time of indifference," utilizing light management as a form of psychological control. (2025). 9781781683101, Verso. ISBN 9781781683101
However, studies have since evaluated the impact of the sleep deprivation imprint on the military culture. Personnel surveys reveal common challenges such as inadequate sleep, fatigue, and impaired daytime functioning, impacting operational effectiveness and post-deployment reintegration. These sleep issues elevate the risk of severe mental health disorders, including PTSD and depression. Early intervention is crucial. Though promising, implementing cognitive-behavioral and imagery-rehearsal therapies for insomnia remains a challenge. Several high-profile military accidents caused in part or fully by sleep deprivation of personnel have been documented. The military has prioritized sleep education, with recent Army guidelines equating sleep importance to nutrition and exercise. The Navy, particularly influenced by retired Captain John Cordle, has actively experimented with watch schedules to align shipboard life with sailors' circadian needs, leading to improved sleep patterns, especially in submarines, supported by ongoing research efforts at the Naval Postgraduate School. Watch schedules with longer and more reliable resting intervals are nowadays the norm on U.S. submarines and a recommended option for surface ships.
In addition to sleep deprivation, circadian misalignment, as commonly experienced by submarine crews, causes several long-term health issues and a decrease in cognitive performance.
Under one interrogation technique, a subject might be kept awake for several days and, when finally allowed to fall asleep, suddenly awakened and questioned. Menachem Begin, the Prime Minister of Israel from 1977 to 1983, described his experience of sleep deprivation as a prisoner of the NKVD in the Soviet Union as follows:
Sleep deprivation was one of the five techniques used by the British government in the 1970s. The European Court of Human Rights ruled that the five techniques "did not occasion suffering of the particular intensity and cruelty implied by the word torture ... but amounted to a practice of inhuman and degrading treatment", in breach of the European Convention on Human Rights.
The United States Justice Department released four memos in August 2002 describing interrogation techniques used by the Central Intelligence Agency. They first described 10 techniques used in the interrogation of Abu Zubaydah, described as a terrorist logistics specialist, including sleep deprivation. Memos signed by Steven G. Bradbury in May 2005 claimed that forced sleep deprivation for up to 180 hours ( days) by shackling a diapered prisoner to the ceiling did not constitute torture, nor did the combination of multiple interrogation methods (including sleep deprivation) constitute torture under United States law. These memoranda were repudiated and withdrawn during the first months of the Obama administration.
The question of the extreme use of sleep deprivation as torture has advocates on both sides of the issue. In 2006, Australian Federal Attorney-General Philip Ruddock argued that sleep deprivation does not constitute torture. Nicole Bieske, a spokeswoman for Amnesty International Australia, has stated the opinion of her organization as follows: "At the very least, sleep deprivation is cruel, inhumane and degrading. If used for prolonged periods of time it is torture."
Other researchers have questioned these claims. A 2004 editorial in the journal Sleep stated that, according to the available data, the average number of hours of sleep in a 24-hour period has not changed significantly in recent decades among adults. Furthermore, the editorial suggests that there is a range of normal sleep time required by healthy adults, and many indicators used to suggest chronic sleepiness among the population as a whole do not stand up to scientific scrutiny.
A comparison of data collected from the Bureau of Labor Statistics' American Time Use Survey from 1965 to 1985 and 1998–2001 has been used to show that the median amount of sleep, napping, and resting done by the average adult American has changed by less than 0.7%, from a median of 482 minutes per day from 1965 through 1985 to 479 minutes per day from 1998 through 2001.
The Guinness World Record stands at 449 hours (18 days, 17 hours), held by Maureen Weston of Peterborough, Cambridgeshire, in April 1977, in a rocking-chair marathon.
Claims of total sleep deprivation lasting years have been made several times, but none are scientifically verified. Claims of partial sleep deprivation are better documented. For example, Rhett Lamb of St. Petersburg, Florida, was initially reported to not sleep at all but actually had a rare condition permitting him to sleep only one to two hours per day in the first three years of his life. He had a rare abnormality called an Arnold–Chiari malformation, where brain tissue protrudes into the spinal canal and the skull puts pressure on the protruding part of the brain. The boy was operated on at All Children's Hospital in St. Petersburg in May 2008. Two days after surgery, he slept through the night.
French sleep expert Michel Jouvet and his team reported the case of a patient who was quasi-sleep-deprived for four months, as confirmed by repeated recordings showing less than 30 minutes (of NREM sleep) per night, a condition they named "agrypnia". The 27-year-old man had Morvan's fibrillary chorea, a rare disease that leads to involuntary movements, and in this particular case, extreme insomnia. The researchers found that treatment with 5-HTP restored almost normal sleep stages. However, some months after this recovery, the patient died during a relapse that was unresponsive to 5-HTP. The cause of death was pulmonary edema. Despite the extreme insomnia, psychological investigation showed no sign of cognitive deficits, except for some .
Fatal insomnia is a neurodegenerative disease that eventually results in a complete inability to go past stage 1 of NREM sleep. In addition to insomnia, patients may experience panic attacks, paranoia, phobias, hallucinations, rapid weight loss, and dementia. Death usually occurs between 7 and 36 months from onset.
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