Lack of sleep: Why is sleep important and how sleep deprivation affects your mind and body

We all know that a lack of sleep can feel horrible, but did you know it could be seriously damaging your health too?

(Image credit: Andrey Bielikov)

There are very few things that will ruin a day like a complete lack of sleep the night before. 

Waking up groggy and bleary-eyed is not how anyone wants to start their day, because dealing with a lack of sleep isn't easy. You might even find yourself looking for more niche solutions to the problem, such as do sleep affirmations work, so when it comes to how to wake up , it doesn't feel like an impossible task.

Sleep deprivation is a real problem that affects approximately one in three people around the world. In the short-term, the side effects will have us reaching for caffeine, which has its own pitfalls, and could leave us vulnerable to viruses – sleep is one of the best natural flu remedies. But it's in the long term that lack of deep sleep starts to really cause problems, for both the mind and body.

Why is sleep important?

As most people sleep for less than the recommended eight hours, it can be easy to see sleep deprivation as normal and forget why it's truly important. As sleep expert James Wilson says, there's basically nothing that goes on in our bodies where sleep doesn't play a vital role.

"Sleep is the foundation that the rest of our health is built upon," He says, "It helps us physically recover and repair from illness and injury, it builds our immune system. It helps clean the brain of neurotoxins that can contribute to Alzheimer’s and Dementia. It makes it easier to stick to healthy eating and our emotional and cognitive health starts with getting the right sleep for us.

"During deep sleep our body repairs itself and that includes any damage to our skin. Good sleep increases blood flow, helps our skin replenish its collagen and repairs damage from the sun. Poor sleep will lead to dark circles under the eyes and more wrinkles and fine lines."

Woman sleeping in bed

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As well having major physical benefits, sleep helps to 're-charge' our brains at the end of each day. As Dr Natasha Bijlani, consultant psychiatrist at Priory Hospital Roehampton says, "Maintaining a regular sleep-wake cycle allows the natural rhythm of the body to be reset every day and therefore optimises brain functioning."

Naturally, this means that a lack of sleep entirely will have a seriously negative affect on our bodies and minds.

How lack of sleep affects your body

A lack of sleep seriously impacts how our body performs throughout the day as if we're tired, we're more likely to struggle with basic functions. However, sleep deprivation can cause serious and long-term physical issues.

Risk of long term health conditions

Arguably one of the most negative impacts of sleep deprivation is how it affects our internal organs. As sleep expert Dr Chris Etheridge explains, "A lack of sleep runs much, much deeper than just feeling tired the next day.

Man sitting on sofa with laptop, researching reasons for a lack of sleep

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"It can impact every aspect of health and wellbeing. From impacting the immune system to a greater risk of depression and anxiety, pain problems and an increased risk of heart disease, diabetes and some cancers."

The risk to those with diabetes is particularly high. A lack of sleep and high blood sugar levels have been linked in people with diabetes, with researchers suggesting that sleep deprivation impacts cortisol and insulin levels. It also may contribute towards oxidative stress.

Having less than six hours sleep per night can also increase the risk of developing diabetes in the first place, since a lack of sleep has been linked to a risk of developing insulin resistance - which could lead to type 2 diabetes.

The NHS highlights the risk of heart disease in those who get less than the recommended sleep. They say, "Long-standing sleep deprivation seems to be associated with increased heart rate, an increase in blood pressure and higher levels of certain chemicals linked with inflammation, which may put extra strain on your heart."

Damage to skin

We've all heard the term 'beauty sleep' but it's more than just a saying, as how many hours and the quality of our sleep can greatly affect our skin.

Research has shown that just a short period of sleep deprivation can lead to swollen eyes, darker under-eye circles, paler skin, as well as more wrinkles and fine lines on the face. This is because our body repairs itself when we're asleep. As we're resting, the skin's blood flow increases and starts to re-build collagen and repair any damage from UV exposure. This helps to naturally reduce the appearance of fine lines and wrinkles.

Woman sitting on the side of the bed, suffering from a lack of sleep

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For similar reasons, it's thought that sleep quality and acne are related. One study found that those who suffer from a lack of sleep were more likely to suffer with acne as sleep deprivation spikes cortisol levels, which in turn leads to inflammation in the body and an increase in sebum production which clogs pores and causes breakouts.

Increased appetite

When we're sleep deprived, our appetite changes and we're likely to eat more food than we normally would. This is due to a disruption in the production of two hormones: ghrelin and leptin.

Ghrelin is a hormone that's produced in the stomach and works by sending hunger signals to the brain, letting it know that food needs to be consumed. Leptin is a hormone released from fat cells and works to suppress hunger and signal fullness to the brain. When someone is sleep deprived, their body produces more ghrelin and less leptin, which means that they're likely to eat more than they otherwise would.

Additionally, there is evidence to suggest that food stimulates the reward centres of our brains more when we're sleep deprived so we're more likely to eat more, in order to feel better. Prolonged sleep deprivation, in turn, would then lead to weight gain and other visible bodily changes.

Decreased sex drive

Feeling like you've gone off sex could be linked to how much sleep you're getting, according to the NHS. "Men and women who don't get enough quality sleep have lower libidos and less of an interest in sex, research suggests."

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One study, for instance, found that men with poorer sleeping patterns have significantly lower levels of testosterone, which will likely result in a lack of sex drive. Researchers also discovered that sleep deprivation is linked to an inability to build enough strength through muscle mass and bone density also leads to low energy levels and fatigue, which could also be contributing to a reduced libido.

Another study looked at the effect of sleep deprivation on women's sex drive and a similar conclusion was reached: women who slept more were likely to have more interest in sex than those who slept less. The research was focused around university-aged women and concluded that even one more hour of sleep per night led to a 14% increase in sex drive.

How lack of sleep affects your mind

Brain fog

Brain fog, highlighted as one of the many long-Covid symptoms at the beginning of the pandemic, is also a common symptom of real sleep deprivation.

Woman sitting at a desk, struggling with brain fog as a result of sleep deprivation

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"Sleep deprivation has a somewhat similar effect as a hangover and disrupts the ability of the brain cells to communicate with each other." Wayne Ross, sleep researcher and advisor at  InsideBedroom, explains.

"This leads to temporary mental lapses that affect memory and visual perception. The work from home trend did not work very well for many during the lockdown, and with it came many changes that disrupted normal sleep patterns."


As burnout is complete emotional, physical and mental exhaustion brought on by stress, it's not surprising that a lack of sleep would be a major contributor to the condition.

"Sleep deprivation can have major repercussions on health and wellness, and poor sleep over extended periods of time has more than often led to burnout." Wayne explains. "Getting less than six hours of sleep each night instead of the recommended seven to nine hours has been known to result in on-the-job burnout. Poor sleep quality over a span of days, or in chronic cases over weeks or months, can cause distress and anxiety when faced with stressful job situations. Reactions can vary from person to person and most often result in compulsive and risky decisions."

Also, while we might think that a strong black coffee is doing us a world of favours when we're tired, that's not actually the case. "Skip caffeine after 2pm as it hits a peak level in your bloodstream within 30 to 60 minutes. It has a half-life of three to five hours (the time it takes for your body to eliminate half of the drug from your system)." Dr Simoné Laubscher, formulator of WelleCo’s The Super Elixir and founder of Rejuv Wellness, says.

Woman napping

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"The remaining caffeine can stay in your body for six+ hours, so I always tell my patients to avoid caffeine after 2pm if you have trouble sleeping. Balance is key, so try to live with healthy boundaries on caffeine and be mindful. Ask yourself if you need or really need this, or are you reaching for a cup out of habit - and therefore potentially reducing the quality of your sleep." 

Mental illness

While sleep deprivation doesn't automatically equate to poor mental health, there is evidence to suggest that the two are linked.

"Ongoing poor sleep can be a huge risk factor for the development of major depressive disorder." Dr Natasha Bijlani says, "The risk of feeling depressed and/or anxious (as well as worsening existing anxiety and depression) increases with the severity of insomnia, and so it is important to recognise and sort out sleep problems as soon as they are identified." 

But she says, "Missed sleep can lead to psychological and physical ill health in many ways." 

Psychological symptoms and effects include:

  • Low mood
  • Anxiety
  • Irritability
  • Erratic behaviour
  • Poor cognitive functioning and performance (eg forgetfulness, making mistakes and slower thinking than normal)
  • Psychotic episodes

Alongside this, there are also the physical manifestations of these problems such as the physical symptoms of anxiety, tiredness, elevation in blood pressure and stress hormones, the negative effects on cardiovascular health and damage to the immune system.


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