Sleep deprivation doesn't just happen when you don't sleep at all for a night or more. Lack of zzz's also adds up through chronic sleep restriction or not getting enough hours per night, or from sleep disruption and poor quality sleep.

All of these factors can lead to real problems that range from merely uncomfortable and inconvenient symptoms of minor sleep deprivation to impairments and health impacts that can be downright dangerous to the person lacking rest and those around them.

Looking Tired

Visible signs of sleep deprivation appear after just one night of poor sleep. Eyes may look red, puffy, or droopy with dark circles underneath, the skin may be pale, and the corners of the mouth droop.

People who slept poorly will often be drowsy and fatigued with less strength and slower responses than usual, and may yawn frequently.

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Memory and Concentration

Adequate sleep is very important to concentration, learning, and remembering. This means that it's difficult to succeed at work, school, or in general daily life without enough sleep for the brain to work properly. Fuzzy thinking only gets more noticeable the worse sleep deprivation becomes.

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Immune System

Adults who get less than seven to eight hours of sleep per night have less ability to fight off infections after exposure and recover more slowly than an adequately rested person.

This is because missing sleep reduces the body's production of antibodies, immune cells, and protective proteins called cytokines, which are all produced mainly during sleep.

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Mood Swings and Irritability

Multiple regions of the brain work together to control mood stability. Sleep deprivation makes this teamwork break down, leading to emotional instability such as mood swings, irritability, impulsivity, increased anger, physical and verbal aggression, anxiety, and depression.

This might show up as general grumpiness or have behavioral consequences like tantrums or getting in fights.

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Accidents and Poor Judgment

Sleep deprivation and drowsiness can cause as much impairment to brain function as some drugs or alcohol, especially when it comes to focus, performance, and judgment. It's estimated that drowsy driving is responsible for at least one million car crashes and 8,000 deaths per year in the United States alone.

This impairment also leads to poor productivity, making bad choices, and errors and accidents in the workplace that, in certain industries, can have life-threatening consequences.

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Depression and Mental Illness

Getting enough sleep is important for mental health. Sleep deprivation causes a significant increase in the frequency and severity of symptoms of mental distress including depression, anxiety, and stress levels.

The odds of frequent mental distress are 2.5 times the rate they would be for someone getting enough sleep. It may also make symptoms of other mental illnesses worse.

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Psychosis and Hallucinations

Prolonged sleep deprivation was historically used as a form of torture for good reason. After as little as 48 hours without sleep, a person may start to experience disordered thoughts, time distortion, and hallucinations such as seeing, feeling, or hearing things that aren't real.

The more time without sleep, the worse symptoms become. After 72 hours, people develop signs that mimic acute psychosis such as delusions, paranoia, and delirium. These symptoms nearly always resolve when normal sleep resumes.

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Insulin Resistance, Diabetes, and Obesity

Sleep deprivation increases the hunger-causing hormone ghrelin, and lowers the hormone leptin, which controls hunger. It also reduces the body's ability to use insulin to process glucose, so it takes longer for glucose to be removed from the bloodstream. This can lead to insulin resistance, a precursor to diabetes.

People who get less than six hours of sleep per night are 1.7 times as likely to have diabetes. Increased hunger, reduced ability to feel satisfied after meals, and a damaged ability to use insulin can all be strong contributors to obesity.

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Hypertension, Stroke, Heart Attack

The cardiovascular system is especially vulnerable to long-term sleep deprivation. Adults who routinely do not get enough sleep are more likely to have high blood pressure and are up to 48% more likely to develop heart disease.

There's also a 45% increase in the risk of a potentially serious heart attack and other dangerous cardiac events, such as a stroke.

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Risk of Death

Getting seven to eight hours of sleep per night has the lowest risk of death from all other unrelated factors. People who get five or fewer hours of sleep per night have a 12% greater risk of death. The largest increase in death among sleep-deprived people is from acute heart attacks, but there is also an increased risk of fatalities from health problems such as cancer or chronic diseases.

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