The impact of sleep deprivation on your mind and body

If you’re not sleeping enough, the effects could be more significant than bags under your eyes, and there could also be dramatic but hidden effects on how you think and feel. Head of Preventative Medicine, Dr Ben Kelly, explains sleep can be closely linked to your physical and mental health.

Effect of sleep deprivation on the body

The rise of obesity over the last few decades is paralleled by significant reductions in the length of time we spend asleep.

At the same time, a large number of studies have reported associations between impaired sleep and the likelihood of developing obesity or diseases such as type 2 diabetes.

But let’s be clear. The act of sleeping less does not in itself make you fat – after a few disturbed nights your body won’t automatically have created fat.

We’re not talking about a cause/effect link here. We’re talking correlation. As the number of people getting less sleep has risen, so the number of people at risk of life-threatening metabolic and cardiovascular diseases has risen too.

How lack of sleep is linked to weight gain, type 2 diabetes and heart problems

The reason for this correlation may lie in the effects that poor quality or reduced sleep can have on your behaviour and physiology. These are the effects that can contribute to weight gain:

  • Inactivity: If you’re feeling lethargic and tired, you’re less likely to exercise and more likely to take shortcuts like using the lift rather than the stairs. This decreases the amount of calories you’re burning, which has a direct effect on your weight.
  • Mood fluctuations: Sleep is vital to regulating your mood. Less sleep could see you happy one moment and feeling low the next. Low mood can trigger emotional or ‘comfort’ eating, when our bodies crave high-fat, high-sugar foods. When eaten, these foods trigger the pleasure response in your brain, and we’re hardwired to crave them in times of distress.
  • Reduced leptin levels: Less of this hormone that tells you you’re full could see you overeating without realising it.
  • Increased grehlin levels: Likewise, more of this hormone that tells you you’re hungry will have you seeking out more food and snacks, even if you’ve consumed the right amount of food for you that day.

If you struggle to cope with these effects, it’s likely you’ll gain weight. And weight gain itself causes serious problems. As your body fat percentage increases, so does your risk of developing metabolic diseases such as type 2 diabetes.

Equally, your cholesterol levels, blood pressure and other risk factors could increase to dangerous levels as you gain weight.

Countering the impact

  • Sleep: Make sure you’re getting enough sleep. For adults, 7–8 hours of sleep per night is associated with the lowest risk of incidence of cardiovascular diseases. See our tips for a good night’s sleep if you’re not sure where to start. If you’re struggling to achieve the full 7–8 hours of sleep per night due to factors you can’t control – a new baby, for example – make an extra effort to maintain a healthy diet and exercise programme, and return to a regular sleep pattern as soon as you can.
  • Stay active: If you really don’t have the energy for the gym, go for a brisk walk around the block to elevate your heart rate slightly.
  • Eat well: Eat three healthy meals a day with a couple of well-chosen snacks. For inspiration, read our nutrition articles.
  • Seek help: If you've realised you're gaining weight and want to explore ways to tackle it, why not speak to a personal trainer or nutritional therapist?

Effects of sleep deprivation on the mind

It’s perhaps not news that too little sleep makes you less mentally acute, and can cause you to feel blue. But what’s happening in your body to cause these feelings?

Hormonal imbalance

We know that a lack of sleep can cause either an excess or a deficit of certain hormones in your body, and we’ve already seen how this can impact things like weight. But hormones control dozens of vital processes, so it’s no wonder that too little sleep can give rise to malfunctions in the way you think (cognition) and your mood (emotional wellbeing).

Worryingly, however, many people still don’t consider a lack of sleep to be a serious condition – it’s just a bad night’s sleep right? But prolonged sleep deprivation can be debilitating, and even cause serious harm to your mental health.

Low mood

During a 2015 sleep study, healthy young adults subjected to partial sleep restriction demonstrated higher levels of cortisol (the stress hormone), particularly in the evening. They also exhibited altered activity in their sympathetic nervous system – the system responsible for the fight-or-flight response. In short, having slept less, the subjects were more ‘on edge’ and stressed.

Prolonged sleep deprivation has also been associated with depression, anxiety, and in extreme cases, thoughts of suicide or self-harm. While these severe cases may have other factors involved, such as poor diet, lack of exercise or substance abuse, emotional distress shouldn’t be ignored. You can begin to tackle stress and low mood by talking through how you're feeling with someone you trust.

If you feel like you can't control your emotions, are having desperate thoughts, or know someone who is, speak to a medical professional in complete confidence today.

Lack of concentration

In one shocking study, conducted in 2000, alcohol was used to illustrate the impact of sleep deprivation on cognitive performance. It found that cognitive ability of someone who’d been awake for 17 hours was the same as a person with a blood alcohol concentration of 0.05% (the legal driving limit in the UK is only slightly higher at 0.08%).

Following 24 hours of wakefulness, performance was equivalent to that with a blood alcohol concentration of 0.1%, well over the limit at which it’s legal to drive.

Staying up all night could be worse than being drunk – so take heed of the signs that say ‘Tiredness can kill.’ Avoid driving or operating heavy machinery and aim for 7–8 hours of sleep per night as soon as you can.

Sleep deprivation has been linked to potentially serious changes to emotion, mood states, and their regulation. What’s more, it could dramatically slow your response time and ability to make rational decisions, placing you and others in harm’s way. Find out more about how sleep impacts your health and how to improve your sleeping environment.

Last updated Friday 8 July 2022

First published on Monday 5 June 2017