of the immune system is one of them. while it is not clearly understood, researchers believe that sleep is essential to providing sufficient energy for the immune system to work and allow inflammation to take place during sleep. also, just as sleep can reinforce memory in a person's brain, it can help consolidate the memory of the immune system or adaptive immunity. an adequate amount of sleep improves 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 were less likely to develop a proper immune response to the vaccine and sometimes even required 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 6 hours a night are more prone to infection and are more likely to catch a cold or flu. a lack of sleep can also prolong the recovery time in patients in intensive care unit (icu). weight gain main article: sleep and weight a lack of sleep can cause an imbalance in several hormones that are critical in weight gain. sleep deprivation increases the level of ghrelin (hunger hormone) and decreases the level of leptin (fullness hormone), resulting in an increased feeling of hunger and desire for high-calorie foods. sleep loss is also associated with decreased growth hormone and elevated cortisol levels, which are connected to obesity. people who do not get sufficient sleep can also feel sleepy and fatigued during the day and get less exercise. obesity can cause poor sleep quality as well. individuals who are overweight or obese can experience obstructive sleep apnea, gastroesophageal reflux disease (gerd), depression, asthma, and osteoarthritis which all can disrupt a good night's sleep. 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. type 2 diabetes it has been suggested that people experiencing short-term sleep restrictions process glucose more slowly than individuals receiving a full 8 hours of sleep, increasing the likelihood of developing type 2 diabetes. poor sleep quality is linked to high blood sugar levels in diabetic and prediabetic patients but the causal relationship is not clearly understood. researchers suspect that sleep deprivation affects insulin, cortisol, and oxidative stress, which subsequently influence blood sugar levels. sleep deprivation can increase the level of ghrelin and decrease the level of leptin. people who get insufficient amount of sleep are more likely to crave food in order to compensate for the lack of energy. this habit can raise blood sugar and put them at risk of obesity and diabetes. in 2005, a study of over 1400 participants showed that participants who habitually slept few 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 which showed that experimental rather than habitual restriction of sleep resulted in impaired glucose tolerance (igt). other effects the national sleep foundation identifies several warning signs that a driver is dangerously fatigued. these include rolling down the window, turning up the radio, trouble keeping eyes open, head-nodding, drifting out of their lane, and daydreaming. at particular risk are lone drivers between midnight and 6:00 am. 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 of shift changes and the findings saw 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. twenty-four hours of continuous sleep deprivation results in the choice of less difficult math tasks without decreases in subjective reports of effort applied to the task. naturally caused sleep loss affects the choice of everyday tasks such that low effort tasks are mostly commonly selected. adolescents who experience less sleep show a decreased willingness to engage in sports activities that require effort through fine motor coordination and attention to detail. great sleep deprivation mimics psychosis: distorted perceptions can lead to inappropriate emotional and behavioral responses. astronauts have reported performance errors and decreased cognitive ability during periods of extended working hours and wakefulness as well as due to sleep loss caused by circadian rhythm disruption and environmental factors. one study has found that a single night of sleep deprivation may cause tachycardia, a condition in which the heartrate exceeds 100 beats per minute (in the following day). generally, sleep deprivation may facilitate or intensify: aching muscles confusion, memory lapses or loss depression development of false memory hypnagogic and hypnopompic hallucinations during falling asleep and waking, which are entirely normal hand tremor headaches malaise stye periorbital puffiness, commonly known as "bags under eyes" or eye bags increased blood pressure increased stress hormone levels increased risk of type 2 diabetes lowering of immunity, increased susceptibility to illness increased risk of fibromyalgia irritability nystagmus (rapid involuntary rhythmic eye movement) obesity seizures temper tantrums in children violent behavior yawning mania sleep inertia sleep deprivation may cause symptoms similar to: attention-deficit hyperactivity disorder (adhd) psychosis assessment patients with sleep deprivation may present with complaints of symptoms and signs of insufficient sleep such as fatigue, sleepiness, drowsy driving, and cognitive difficulties. sleep insufficiency can easily go unrecognized and undiagnosed unless patients are specifically asked about it by their clinicians. 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 diaries are useful in providing detailed information about sleep patterns. they are inexpensive, readily available, and easy to use. the diaries can be as simple as a 24-hour log to note the time of being asleep or can be detailed to include other relevant information. sleep questionnaires such as the sleep timing questionnaire (stq) can be used instead of sleep diaries if there is any concern for patient adherence. actigraphy is a useful, objective wrist-worn tool if the validity of self-reported sleep diaries or questionnaires is questionable. actigraphy works by recording movements and using computerized algorithms to estimate total sleep time, sleep onset latency, the amount of wake after sleep onset, and sleep efficiency. some devices have light sensors to detect light exposure. management although there are numerous causes of sleep deprivation, there are some fundamental measures that promote quality sleep as suggested by organizations such as centers for disease control and prevention, the national institute of health, the national institute of aging, and the american academy of family physicians. the key is to implement healthier sleep habits, also known as sleep hygiene. sleep hygiene recommendations include setting a fixed sleep schedule, taking naps with caution, maintaining a sleep environment that promotes sleep (cool temperature, limited exposure to light and noise, comfortable mattress and pillows), exercising daily, avoiding alcohol, cigarettes, caffeine, and heavy meals in the evening, winding down and avoiding electronic use or physical activities close to bedtime, and getting out of bed if unable to fall asleep. for long term involuntary sleep deprivation, cognitive behavioral therapy for insomnia (cbt-i) is commonly recommended as a first-line treatment, after exclusion of physical diagnosis (f.e. sleep apnea). cbt-i contains five different components: cognitive therapy, stimulus control, sleep restriction, sleep hygiene, and relaxation. these components together have shown to be effective in adults, with clinical meaningful effect sizes. as this approach has minimal adverse effects, and long-term benefits, it is often preferred to (chronic) drug therapy. there are several strategies that help increase alertness and counteract the effects of sleep deprivation. caffeine is often used over short periods to boost wakefulness when acute sleep deprivation is experienced; however, caffeine is less effective if taken routinely. other strategies recommended by the american academy of sleep medicine include prophylactic sleep before deprivation, naps, other stimulants, and combinations thereof. however, the only sure and safe way to combat sleep deprivation is to increase nightly sleep time. uses to facilitate abusive control sleep deprivation can be used to disorientate abuse victims to help set them up for abusive control. interrogation sleep deprivation can be used as a means of interrogation, which has resulted in court trials over whether or not the technique is a form of torture. 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: in the head of the interrogated prisoner, a haze begins to form. his spirit is wearied to death, his legs are unsteady, and he has one sole desire: to sleep... anyone who has experienced this desire knows that not even hunger and thirst are comparable with it. 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 ... 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 (7+1⁄2 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 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 thus: "at the very least, sleep deprivation is cruel, inhumane and degrading. if used for prolonged periods of time it is torture." treating depression further information: sleep deprivation therapy studies show that sleep restriction has some potential in treating depression. those with depression tend to have earlier occurrences of rem sleep with an increased number of rapid eye movements; therefore, monitoring patients' eeg and awakening them during occurrences of rem sleep appear to have a therapeutic effect, alleviating depressive symptoms. this kind of treatment is known as wake therapy. although as many as 60% of patients show an immediate recovery when sleep-deprived, most patients relapse the following night. the effect has been shown to be linked to an increase in the brain-derived neurotrophic factor (bdnf). a comprehensive evaluation of the human metabolome in sleep