Exactly what happens to the body when you pull an all-nighter

EXCLUSIVE Experts reveal the chaos that unfolds inside the body when you go just one night without sleep

  • Just one night of sleep deprivation causes impaired thinking and irritability
  • Avoiding caffeine and technology before bed can help facilitate quality sleep
  • READ MORE:  Five signs you’re not getting enough sleep

Anyone who has ever gone without a good night’s sleep will remember the struggles they experienced the next day.

You feel confused, delirious, emotional and are barely able to function. On occasion, side effects of poor sleep can be similar to a bad hangover, causing nausea and headaches.

And to think, all you’ve done is go without sleep. But, given the cascade of harms bubbling away inside the brain and body as you lay awake, the sober hangover is hardly surprising.

Speaking to DailyMail.com, experts have detailed the intriguing biological processes that play out when we can’t sleep – whether it’s just a late night, staying awake for 24 hours or several days without shut eye.

They describe the chaos as a ‘ripple effect’ – with one malfunction triggering another, followed by another.

Studies have long shown a chronic lack of sleep can increase the risk of a range of conditions, like obesity, memory loss, diabetes, heart disease, and a reduced immune response, leaving you vulnerable to infections. 

Sleep deprivation can lead to obesity, memory loss, diabetes, heart disease, heightened and unstable emotions, impaired ability to learn and a reduced immune response, leaving you vulnerable to disease

But now, specialists have revealed just one night without sleep is enough to cause harm, which should be expected, given sleep is crucial for nearly every bodily function, like regulating hormones, repairing tissues and maintaining a healthy weight. 

So where does it begin?


The effects of not sleeping begin to sink in after 18 hours of being awake, according to experts. This is the equivalent of going to bed at 2am if you woke up at 8am the day before.

Eighteen hours without sleep is when blood pressure will begin to rise, making the heart work harder and putting extra strain on the organ.

In those with underlying cardiac conditions, this could increase the likelihood of a heart attack or stroke.  A 2014 study found heart attacks rose by 25 percent the Monday after daylight saving time, when the clocks spring forward and you lose an hour of sleep.

On the Monday after the clocks go back, heart attacks decline by 21 percent, research shows.

Being awake for more than 18 hours also sees falling testosterone – the male sex hormone. 

Energy levels decline, as do the immune system’s defenses. Just one week of fewer than five hours of sleep per night — or being awake for 19 hours — saw a young man’s testosterone drop by 10 to 15 percent, compared to the normal rate of one to two percent per year. 

Sleep plays a major role in the regulation of hormones, and when the body isn’t getting enough, it can’t carry out its normal functions properly.  

Also around this time, the immune system will begin building up inflammatory proteins associated with heart and chronic disease, and our natural ‘fighter’ cells that combat bacteria and viruses become less effective. 

Dr Andrey Zinchuk, a Yale Medicine pulmonary, critical care, and sleep medicine specialist, told YaleMedicine: ‘I think of every hour of sleep as putting money into a ‘sleep’ savings account. 

‘If your ‘sleep’ savings account is depleted or overdrawn, it will negatively affect your brain and how you interact with the world.’


Twenty-four hours without sleep has a similar effect on the brain as drinking four glasses of wine or beer, according to the Centers for Disease Control and Prevention.

It means you may have reduced reaction times, slurred speech and slowed thinking. 

Other symptoms include irritability, increased stress, impaired concentration and food cravings.

Dr Carolyn Williams, a registered dietitian and author of Meals That Heal, told DailyMail.com that being sleep-deprived also impacts your ability to choose healthy food.

A 2015 study found that for every hours teens lost sleep, they ate 210 more calories the next day, most of it from fat and carbohydrates. Teens with inconsistent sleep patterns were also more likely to snack.

Dr Williams said lack of sleep alters brain function, impacts the foods you crave, how the body regulates hormones and how the body processes foods — making you crave foods you normally wouldn’t. 

Williams added that with a lack of quality sleep, the reward center in your brain is triggered more by food and a recent study showed tired people reacted more to junk foods and were willing to spend more money on them than healthy alternatives. 

After 36 hours of no sleep, any symptoms you’ve been experiencing will worsen. You may also experience microsleeps, brief periods of involuntary sleep lasting up to 30 seconds. 

Dr Martina Vendrame, neurologist and sleep medicine physician at Lehigh Valley Health Network, told DailyMail.com: ‘Missing out on sleep doesn’t just make you tired — it can mess with your schoolwork, job and connections with others. It’s like a domino effect’

During microsleeps, you seem awake and your eyes are open, but your brain ‘turns off’. 

Studies have shown brain activity slows down, preventing you from processing information.

Without sleep, the brain attempts to cope without having had the time it needs to repair itself, leading to extreme stress and impaired performance. 

At 36 hours awake, different parts of the brain struggle to communicate with each other.

It means memory, learning, decision making and reacting all become difficult. 

Also, your blood pressure and heart rate will rise, your metabolism will slow and your heart will be forced to work harder.


Another 12 hours without sleep will take you to what is considered extreme sleep deprivation.

It is likely that the frequency of microsleeps increases. After 48 hours awake, you may hallucinate and experience heightened stress, depersonalization, anxiety and increased irritability.

The brain’s amygdala – which helps regulate mood and memory – and prefrontal cortex – which controls executive function and impulse control – are both severely impaired. 

Dr Scott Lyons, a licensed psychologist, told DailyMail.com that the impact on the amygdala causes people to be 60 percent more reactive in situations of stress or discomfort.

After 72 hours of no sleep, the brain is severely struggling to cope with exhaustion, which could lead to hallucinations, delusions and disordered thinking. 


At 96 hours of sleep deprivation, the risk of psychosis surges. 

This is when you experience an altered perception of reality and may suffer elaborate delusions, as well as severe mood swings.

Sleep deprivation psychosis usually resolves once you get enough sleep. 

However, extreme repeated sleep deprivation can be fatal. 

Extreme fatigue is a major factor in traffic accidents, as well as deadly mistakes in the workplace.

Jessica Tapia, a 29-year-old mother of five kids from 10 years to three weeks old, told DailyMail.com she has slept roughly four to five hours per night for the best part of a decade. 

She is often ‘irritable and very grumpy,’ according to her husband, and sometimes suffers dizziness, brain fog and trouble making decisions.

Ms Tapia, owner of a digital marketing agency, told this website: ‘Sleep deprivation is such a real thing and it can make you feel crazy. 

‘Some mornings I wake up and feel so lightheaded and dizzy to the point where I cannot move… and my husband would have to take our son [and feed him].

‘The scariest thing is that I feel like one day I’m just not going to be aware of what’s going on.’

Sleeping like you are in outer space is a little-known secret to getting an amazing night’s sleep here on Earth, doctors say 

Aside from physical issues that may be causing sleep problems, a person’s mental health also plays a large role in sleep quality.

Dr Lyons told DailyMail.com mood disorders, such as bipolar, depression or generalized anxiety disorder, could all mess with a person’s sleep routine. Poor sleep can also exacerbate mental health issues.

In these cases, it may be helpful to seek out psychological therapy or begin taking medications.

When you sleep, the body goes through four stages: Non-rapid eye movement (NREM) Stage 1, 2 and 3, and rapid-eye movement (REM).

NREM Stage 1 is the transition between being awake and falling asleep and usually lasts between five and 10 minutes.

Your body then moves into stage 2 — when the body’s temperature drops and heart rate slows. This marks the start of sleep spindles— a hallmark of NREM believed to control sleep-related functions such as memory consolidation and brain development. This stage typically lasts 20 minutes.

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NREM 3 sees muscles relax, blood pressure and breathing rate drop. This is when the deepest sleep occurs. In this stage, cells repair and rebuild, hormones are secreted to promote bone and muscle growth and immunity is strengthened. Your brain also cements information into memory — making this type of sleep vital to learning.

After NREM 3, stage 2 is then repeated before falling into REM sleep.

In REM sleep, the brain becomes active, the body relaxes and dreams occur.

Controlling these processes is the circadian rhythm – or the body’s internal clock. 

This helps regulate sleep-wake cycles, ensuring sleep occurs at night and wakefulness occurs during the day.

 Disruptions to this rhythm, such as shift work, jet lag or general trouble sleeping can lead to sleep disorders and impact overall health.

The sleep experts DailyMail.com spoke to recommended going to bed earlier, avoiding caffeine in the afternoon, lowering the temperature in your bedroom and avoiding electronics just before bed as ways to improve sleep health. 

Dr Emer MacSweeney, a neuroradiologist and CEO at Re:Cognition Health, a cognitive care clinic, told DailyMail.com: ‘Sleep deprivation has been linked [to] a myriad of health issues and diseases. Sleep is essential for supporting cognition… memory, language, speech, planning and many other skills.

‘Sleep deprivation has far-reaching consequences on the body and min

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