Sleep and mental health: How does tiredness affect the brain?

Consultant Health Psychologist Dr Sue Peacock from BMI The Saxon Clinic explains how sleep – or lack of sleep – can affect our mental health and wellbeing.


Do you often forget things that you’re sure you know? Do you find it hard to concentrate on complex assignments? Do you struggle with your moods?

If the answer to any of these is ‘yes’, you should ask yourself another question: Do you get less than six hours of sleep a night?

Many people don’t realise, but getting too little sleep can be to blame for all of these issues.

That’s right: lack of sleep can hinder you from thinking clearly and keeping your emotions at an even keel.

Sleep is a necessity, not a luxury

People don’t tend to value sleep, and most people who don’t get enough sleep don’t realise the effects it can have on their health – in particular their cognitive and mental wellbeing.


Many people think of sleep simply as a luxury – a little downtime. They know they feel better when they have had a good night’s sleep, and worse when they haven’t.

But it’s important to recognise that sleep is actually a necessity. A regular sleep pattern improves learning, memory and insight as well as helping our bodies to self-regulate.1

Lack of sleep can cause both psychological and physical problems. One night of disturbed sleep might make you feel foggy, but the long-term effects of sleep problems can be very serious.

Excessive sleepiness has been shown to hurt work performance,2 wreak havoc on relationships, and lead to mood problems such as anger and depression.1

Lack of sleep can alter your mood significantly

Sleepiness slows down your thought processes

Scientists measuring sleepiness have found that sleep deprivation leads to lower levels of alertness and concentration.3 It’s more difficult to focus and pay attention, so you’re more easily confused.


Sleepiness also impairs judgment. Making decisions is more difficult because you can’t assess situations as well and pick the right behaviour.3

Excessive sleepiness impairs memory


Research suggests that the nerve connections that make our memories are strengthened during sleep because sleep embeds the things that we have learned and experienced over the course of the day into our short-term memory.

It is believed that different phases of sleep play different roles in consolidating new information into memories. If your sleep is cut short or disrupted, it interferes with these cycles.

When you’re sleepy, you may forget and misplace things often. And the inability to focus and concentrate caused by sleepiness further weakens memory.


Poor sleep makes learning difficult

Sleep deprivation affects your ability to learn in two ways.

Firstly, because you can’t focus as well, it’s more difficult to pick up information, so you can’t learn efficiently.

Secondly, it affects memory, which is essential to learning.

Sleep is crucial to children as well as adults. In younger children, sleepiness can lead to hyperactivity, which can hinder learning.5

Sleep deprived teenagers may lose the focus, diligence, and memory capacity to perform well in school.6

The biggest danger of sleepiness: Slowed reaction time

Sleepiness makes your reaction time slower, which is a significant problem when driving or when doing work or other tasks that require a quick response. Research suggests that approximately 20% of road traffic accidents are related to lack of sleep.7


You don’t need to fall asleep at the wheel to be a danger. Drowsiness alone can be as dangerous as driving drunk. Driving while sleepy is like driving with a blood alcohol content which is over the legal limit.8

Unsurprisingly, the combination of drinking and drowsiness means double trouble when it comes to driving. Sleep deprivation actually magnifies the effects of alcohol.9

The people at the highest risk of fatigue-related car accidents are teenagers and young adults, especially men.

Shift workers who work at night or work long or irregular hours and people with untreated sleep disorders such as sleep apnoea and narcolepsy are also at high risk.

Excessive sleepiness endangers you and others around you

A slowed reaction time when driving is only one way that excessive sleepiness can endanger you and others around you. When you haven’t had enough sleep, even tasks you are used to can become dangerous.

One study found that sleep deprivation hampered information-integration. This is a function of the mind that relies heavily on split-second, gut-feeling decisions.

The researchers noted that this could be a particular concern for firefighters, police officers, soldiers, shift workers, health care workers and others who are often sleep deprived on the job.10

The Impact of sleepiness on mood and mental health

Lack of sleep can alter your mood significantly. It causes irritability and anger and may lessen your ability to cope with stress.

The “walking tired” are more likely to sit and seethe in traffic jams and quarrel with other people.

Studies show that sleep-deprived people are also less likely than those who sleep well to exercise, eat healthily, have sex and engage in leisure activities.1

Lack of sleep and depression are so closely linked that specialists aren’t always sure which came first

Over time, impaired memory, mood, and other functions become a chronic way of life. In the long term, this can affect your job and relationships.

Sleep and mental health problems

Mental illness and sleep problems are closely linked. If you have sleep issues, you are more likely to have mental health problems, and vice versa.

Sleep and mood affect each other, so it’s common for people who don’t get enough sleep to be depressed or for people who are depressed to not sleep well enough.


Chronic sleepiness puts you at greater risk for anxiety and depression. They are so closely linked that sleep specialists aren’t always sure which came first in their patients.

Often, people who suffer with sleep issues or disorders will have some form of anxiety about sleep. They don’t sleep, so they get anxious about going to sleep and that anxiety stops them sleeping. It’s a self-fulfilling prophecy and a vicious circle.11

How to establish a regular sleeping pattern

As you can see, lack of sleep affects our mental health in terms of feelings and emotions as well as our ability to perform cognitive tasks.

It is absolutely worth taking the time to improve your sleep and establish a healthy sleeping pattern. Here are some simple suggestions to get you started:

10 tips to help you sleep better

1. Go to bed earlier


It sounds simple, but many people go to bed too late to fit in enough sleep.

2. Keep your bedroom free of distracting technology

Establishing your bedroom as a place for sleep – rather than recreation – can help you to sleep better.

3. Turn off devices 30 minutes before bed

Electronics emit a type of light that can keep you awake longer. Turning them off 30 minutes (or an hour) before bedtime can help your body wind down.

4. Avoid alcohol

You may think that drinking alcohol helps you sleep but actually it can interrupt your sleep and wake cycle, meaning you’ll be less rested.

5. Avoid caffeine in the evening

Caffeine is a stimulant that can stop you from falling asleep. Try avoiding caffeinated drinks as much as possible in the evening and even the afternoon.

6. Don’t eat a large meal before bed

If you’re still digesting food when you go to bed, it may stop you from falling asleep.

7. Don’t exercise too close to bedtime

People who exercise more tend to sleep better, however exercising too close to bedtime can keep you up. Only some people are affected but it’s something to watch out for.

8. Keep your bedroom cool and dark

Dark, cool and quiet environments help most people to sleep better. It’s not the same for everyone, so it’s worth experimenting if these conditions don’t seem to work for you.

9. Establish a sleep routine and stick to it

So many people don’t do this but it really works. Keeping regular hours helps you sleep better.

10. Speak to a specialist

If you are having serious problems sleeping and the above methods aren’t helping, a psychologist or sleep specialist can help you identify the causes and start working to fix your sleep patterns.

To find out more call us on 0808 101 0337

or make an online enquiry.



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