What Happens To The Body After Sleep Deprivation

sleep deprivation hallucinations

Remember when the CIA subjected Guantanamo Bay detainees to 11 days of sleep deprivation? According to the U.S. Justice Department, sleep deprivation studies showed that ‘little seem[s] to go wrong with the subjects physically.’

So does that mean it is ok to go without sleep?

Experts say no.

Extended periods of sleep deprivation can cause physical and mental symptoms that affect our health and wellbeing, and even cause sleep deprivation hallucinations.

These effects start as we approach the first 24 hours of sleeplessness, and become more damaging the longer we lose sleep.

Here we explore the health consequences of lack of sleep, and why it is important to get sleep on a regular basis.

What Happens To The Body After Sleep Deprivation

What Is Sleep Deprivation

Sleep deprivation is very different to pulling an all-nighter when we’re trying to meet a deadline. It’s different to missing one or two nights of sleep due to short term stress.

Chronic partial sleep deprivation is when we fail to get enough sleep on a regular basis.

And it’s surprisingly common. The Centers for Disease Control and Prevention (CDC) tells us that almost 35% of American adults don’t get enough sleep on a consistent basis.

But how long can we go without sleep? And what happens to our minds and bodies when we subject ourselves to sleep deprivation for days on end?

lack of sleep hallucinations

How Long Can You Go Without Sleep

The longest a person has gone without sleep is 264 hours (or 11 consecutive days) according to records. We don’t know exactly how long a human can survive without sleep.

What we do know is that within 24 hours, humans begin to feel the effects of sleep deprivation. Within a few days, we might experience hallucinations due to lack of sleep.

Some other effects of sleep deprivation are:

  • Paranoia
  • Irritability
  • Delusions and hallucinations
  • Cognitive impairments
  • Lack of productivity
  • Inability to concentration

And although we don’t know the full impact of long-term sleep deprivation, one study shows that it can kill us.

Health Implications of Sleep Deprivation

After 24 hours

It is fairly common to miss the first 24 hours of sleep. You may be inundated with work, be racing to meet a deadline, studying for an exam, or taking care of a child with a tummy bug. It’s not fun—but it doesn’t create any issues in the body that a nap can’t fix.

Studies show, though, that staying up for 24 hours straight is the equivalent to having a blood alcohol level of 0.10 percent. In many countries, you would be over the legal limit to drive.

After 24 hours of sleeplessness, you might notice:

  • Impaired judgement and decision-making
  • Decreased hand-eye coordination
  • Visual impairment or difficulty focusing
  • Muscle tension
  • Tremors in your arms or legs
  • Reduced reaction speed

After 36 hours

If you’ve been awake for 36 hours, you’re entering the danger zone. Your internal body clock becomes confused, and levels of stress hormone—cortisol—in your blood are likely to be elevated, which can have damaging effects on your physiology over time.

The chemical processes impacted by your internal body clock might start to affect your appetite, slow your metabolism, and lower your internal body temperature.

After 36 hours of sleeplessness, you might notice:

  • Speech impairment, or an inability to choose the right words to communicate.
  • Poor reasoning
  • Inability to concentrate
  • Poor decision-making
  • Lack of motivation
  • Extreme muscle fatigue


After 48 hours

A full two days and nights of missed sleep puts you at risk of serious injury. Your body will have difficulty staying awake at this point, and may go into a state of ‘microsleep.’ Microsleep is an involuntary process where your brain rests itself for up to 30 seconds, regardless of what your body is doing at the time.

If you are at home sitting on the sofa when this happens, you may just feel slightly disorientated. If you are driving, using a hot stove, or caring for someone else at the time, the repercussions can be much worse.

After 48 hours of sleeplessness, you might notice:

  • A worsening of earlier symptoms.

What you won’t notice is the disruption happening within your immune system. Natural killer cells—which your body sends out to respond to viruses and bacteria that threaten your health—have started to reduce their activity at this point, and inflammation is increasing.

After 72 hours

Most people are unable to stay awake on their own after 72 hours without sleep. You are likely to have experienced microsleep—maybe many times—at this point.

Most people will struggle to perform basic tasks without difficulty. Multi-tasking, memory recollection, and attention to detail may be non-existent.

After 3 days of sleeplessness, you might notice:

  • Feelings of depression, anxiety, or paranoia
  • Unreasonable anger or aggression
  • Inability to feel empathy or to consider others
  • Difficulty holding a conversation
  • Impaired senses—sight, hearing, and smell might be dull

One study also showed that after 30 hours of sleep deprivation, participants were unable to identify happy or angry facial expressions.

After being deprived of sleep for this long, you will also experience a massive impact on your perception. Both depth perception—or the distance you perceive yourself to be from an object or place—and visual perception are affected. Sleep deprivation hallucinations are common, and an inability to differentiate between what you see and what you think you see can have drastic effects on mental health.


Common Symptoms of Sleep Deprivation

Short-term sleep deprivation has many symptoms, both cognitive and physiological:

Cognitive Symptoms of Sleep Deprivation

  • Difficulty staying alert
  • Difficulty concentrating or focusing
  • Poor memory and inability to retain new information
  • Drowsiness
  • Irritability
  • Anxiety and depression
  • Fear
  • Reduced productivity

Physiological Symptoms of Sleep Deprivation

Although the physiological symptoms are difficult to see immediately, sleep deprivation has been known to influence:

  • Reduced immune system functioning
  • High blood pressure
  • Stroke
  • Obesity
  • Type 2 diabetes
  • Heart disease
  • Depression and anxiety

How much sleep do you really need?

Some of us need more sleep than others, but the recommended minimum—according to the CDC—is 7 hours for adults.

Over a third of us do not get that much sleep on a regular basis.

The CDC also recommends that adults do not stay up longer than 17 consecutive hours, since we are likely to begin to experience symptoms of sleep deprivation past this point.

 health consequences of lack of sleep

How can you improve your sleep quality?

Understanding the effects chronic partial sleep deprivation can have on our bodies and minds, and knowing how much sleep we should be getting each night, are a start.

But how can we begin to improve our sleep hygiene?

There are several steps we can take to improve the length of time we spend asleep, and the quality of our sleep each night:

1. Avoid caffeine and other stimulants.

Stimulants like caffeine and nicotine can keep us awake when we should be winding down, and reduce our perception of how tired we really are. Cutting out coffee for at least 3 hours before bed is a good start, although some experts recommend that we avoid coffee up to 7 hours before bed.

2. Avoid alcohol before bed.

Alcohol is widely acknowledged to help you fall asleep faster, because it is a depressant. Too much of it can affect our sleep quality, as the body has to begin processing the alcohol instead of putting your energy and hydration stores into recovering other systems.

3. Limit daytime naps.

Despite popular belief, a ‘power nap’ is not as good for you as a proper night’s rest. A short nap of 20-30 minutes can, however, improve your mood, alertness, and performance in the short-term.

4. Get some exercise.

Exercise in the morning is beneficial to our body and mind in many ways. Aerobic exercises—like walking, running, and swimming—can also help oxygenate our bodies and improve the quality of rest we get at night.

It’s important to avoid moderate to intense exercise at night, since this may leave your body and mind more stimulated and energized, which will make it difficult to fall asleep.

5. Choose the right foods.

That feeling of wanting a nap after you eat a heavy meal doesn’t necessarily mean you’re eating the right foods for sleep hygiene. Heavy, rich, fatty, or fried foods can trigger indigestion, make falling asleep uncomfortable, and put strain on your digestive system as you rest.

Citrus fruits, fizzy drinks, and spicy foods can also cause painful heartburn.

6. Expose yourself to natural light.

Our internal body clock requires vitamin D, which our body can generate by getting enough sunlight in the daytime. Sunlight during the day, and darkness at night, can also help us regulate our sleep patterns.

7. Create a good sleep environment.

One study has shown that replacing your mattress can improve sleep quality by 62%.

A cool sleeping environment is also best for our sleep hygiene—between 60 and 67 degrees Fahrenheit, to be exact.

8. Establish a routine.

A regular night-time routine can help our mind and body prepare for sleep. You could introduce several steps to your routine, leading up to going to sleep:

  • Take a warm bath or shower.
  • Go through a skincare or haircare routine following your shower.
  • Do some light stretching.
  • Put away electronics.
  • Read or practice simple mindful exercises.
  • Turn your light out at a specific time.


Why Lack of Sleep Causes Hallucinations

Although it’s not completely understood how lack of sleep causes hallucinations, researchers belief it is a combination of elevated cortisol and adrenaline levels, coupled with reduced cognitive function and episodes of microsleep.

20 studies demonstrated that where participants were deprived of sleep for between 24 hours and 11 days, with an average of 92 hours without sleep, the participants reported perceptual changes.

These perceptual changes included visual distortion—where 90% of the participants were unable to recognize familiar objects, or identified the objects incorrectly. Some reported sensory and auditory distortion—they misinterpreted sounds, or reported sounds that nobody else could hear.

These symptoms occurred within 24-48 hours of sleep loss, and advanced to complex hallucinations and delusions within 48-90 hours. After 72 hours, research noted, the participants displayed symptoms of acute psychosis or toxic delirium.

A period of normal sleep helped to resolve the symptoms in many of the cases—but not all of them.


There are no health benefits of sleep deprivation. It can have a serious impact on our mental and physical health, but only two thirds of American adults are getting enough sleep.

health benefits of sleep deprivation

Good sleep hygiene, and aiming to get the right amount of sleep for our age, can reduce our risk of cardiovascular disease, diabetes, obesity, and mental illnesses—including hallucinations and acute psychosis.