Stress and brain function: how too much stress affects your brain

Stress is a normal part of life for most people – but when it becomes frequent or overwhelming, the effects can reach further than you might expect. From racing thoughts and poor sleep to changes in concentration and mood, the brain can be one of the first places to show us we need to slow down. With insight from Heeral Tomlinson in the H&B Science team, we’ll explore what stress does to the brain in the short and long term and the steps you can take to help look after your mind...

“When we experience stress, the brain helps activate the body’s stress response, involving hormones such as adrenaline and cortisol (the ‘stress hormone’)," says Heeral.^1,2 These help release fast-acting energy needed for the 'fight or flight' response.¹ This might not be so useful if you're stressed about something like an upcoming test. But it's not totally pointless: “in the short term, this helps us respond to a challenge and can increase alertness.” These hormones also reserve energy in places the brain decides is less important, for example in digestion. That's why you might get a funny tummy in times of stress.

Even in the short term, stress can negatively impact your brain. “Stress can affect processes such as attention and memory,” Heeral explains – that’s why you might feel flustered and unable to focus on a hectic day. Long-term stress can also affect the brain's neuroplasticity (its ability to adapt and form new connections).³ Many different parts of the brain play a role in the stress response, including: ^2,4

• the prefrontal cortex: responsible for cognitive function and emotional and behaviour regulation ⁵

• the hippocampus: a seahorse-shaped structure that helps form and retain memories ⁶

• the amygdala: involved in emotional processing and attaches emotional meaning to memories ⁷

Because these areas are involved in things like memory, thinking and emotional processing, it helps explain why stress can show up in different ways – from struggling to focus to feeling more emotionally overwhelmed. Some of these reactions happen instantly, and others take place minutes or hours later – the brain may still produce more cortisol up to an hour after a stressful event.² So even once the moment's passed, you might feel wired for a while.

Chronic (long-term) stress may have longer-lasting effects on the brain. “Long-term or repeated stress has been associated with changes in the way areas of the brain involved in memory, learning and emotional regulation function," Heeral says.⁴ Over time, repeated activation of the body's stress response can contribute to what's known as 'allostatic load' – essentially the cumulative strain of repeatedly adapting to stress.⁴ It's not just stressful emotions that can contribute to allostatic load: unhealthy habits like smoking, alcohol overuse, a poor diet or sleep deprivation may be stressful for the brain.⁴

You may also have heard that chronic stress increases your risk of certain neurodegenerative (brain-deteriorating) conditions later in life. In a 2020 study funded by the Alzheimer's Society, researchers found that people with mild cognitive decline had higher stress levels than healthy individuals. However, the amount of stress a person felt did not correspond to how much their thinking abilities declined over time.⁸ But as Heeral explains it: "brain health is influenced by many different factors, so stress is only one part of a much bigger picture."⁴

Sometimes, you might not realise how much of a toll your worries are taking on you – until you spot other changes in your mood or behaviour. Here are some tell-tale signs that stress may be affecting your mind...

You’re struggling to concentrate

When something’s stressing you out, it can be difficult to shift your attention away from it and focus on what’s in front of you. Research suggests stress can affect thinking skills including attention and working memory, which may help explain why concentrating can feel that little bit harder under pressure.²

You're more forgetful than usual

We all have forgetful moments, but stress may make them more likely. When you’re under pressure, it can be harder for your brain to store and retrieve certain memories, and research suggests stress may also affect activity in the prefrontal cortex – an area involved in cognitive function.^9,10,11 So, whether your mind goes blank in a big meeting or you lose your train of thought halfway through a task, stress could be one factor at play. However, you should speak to a GP if your forgetfulness is affecting your day-to-day life.¹⁰

You're feeling irritable

Find yourself snapping at people? Stress can leave you feeling more irritable or emotionally overwhelmed, so everyday frustrations may feel harder to handle than usual. If little things are getting to you more than usual, stress could be playing a part.

Try to be kind to yourself and give yourself space to notice what’s triggering your frustration before reacting. Practicing mindfulness and breathing exercises may also help you feel calmer and manage your emotions.¹² Irritability should subside once your stress decreases, but if your frustration's affecting your self-esteem or your relationships, it's worth speaking to a GP for help.¹²

You're relying on unhealthy habits

Maybe you feel tempted to restart coping mechanisms, like alcohol or smoking, when life feels tough. While they might feel helpful in the moment, they can ultimately leave you feeling worse and may have negative effects on your physical and mental health.¹³ If you've noticed yourself slipping into old habits or craving something you previously managed to kick, ask yourself if stress is playing a role and consider seeking professional help.¹³

“Looking after the basics can be particularly important during stressful periods. Regular physical activity, getting enough good-quality sleep, eating a balanced diet, taking time to unwind and staying connected with others can all support our overall physical and mental wellbeing," says Heeral.¹⁴ So when life feels a little more stressful than usual, these are some of the basics worth coming back to...

Get plenty of sleep

Stress and sleep can be a tricky combination. Not getting enough sleep may make stress harder to deal with, while feeling stressed can make it harder to drift off – or leave some people sleeping more than usual.^15,16,17 Sleep also plays an important role in processes like emotional processing and memory formation.¹⁶ If stress is disrupting your sleep, try to stick to a regular sleep routine where you can and give yourself permission to rest when you need it.

Exercise regularly

Exercise might feel particularly tough when you're having a difficult time, especially if you're getting physical side effects of stress like headaches or fatigue.¹⁸ However, regular movement helps produce endorphins that make you feel good and may help you clear your head.¹⁹ That doesn't have to mean a stereotypical gym workout: a stroll in nature, a dance class or a yoga session can all get your body moving and your 'happy hormones' flowing. Take things at your own pace and bring a friend if you'd like.

Eat a balanced diet

Eating well can also be particularly difficult in times of stress. You might not have the time or motivation to cook, or you might only want limited types of foods. If cooking feels like a lot, take the pressure off making every meal 'perfect'. Simple, nourishing options still count. A varied and nutritious diet helps provide a steady source of energy and contains vitamins that help support areas like normal mood, energy and cognitive function.

Your brain and gut communicate directly and certain 'happy hormones' like serotonin are primarily made in the gut – so what you eat may play a role in your overall wellbeing.²⁰ Looking for inspiration? A diet like the Mediterranean diet focuses on fruit and vegetables, lean protein, sources of healthy fats, fibre and whole grains.²¹ You could also consider batch cooking nutritious meals on days where you're able and freezing them for more difficult days. Bonus points for focusing on nutritious food you actually enjoy – no one wants to force down a meal they don’t fancy after an already stressful day.

Stay connected with friends

Stress can make it tempting to retreat from everyone, but staying connected can make difficult periods feel a little less lonely. That doesn't have to mean a big day out – it could be a friend popping over for a cup of tea or a quick phone call. If you feel comfortable, let people close to you know what's going on so they know when you might need a little extra support.

Maintain a routine

When other parts of life feel unpredictable, a little structure can help things feel more manageable. A routine can help reduce 'mental load', so try pencilling in the basics – meals, movement, time to unwind or seeing someone you love – but don't turn your routine into another source of pressure. If it starts to feel overwhelming, scale it back.

Sometimes looking after the basics isn't enough and you need something that helps in the moment. From slowing your breathing to switching off your notifications, here are a few techniques to try when stress starts to feel overwhelming...

Try mindfulness or breathwork

If stress feels overwhelming or it's making you anxious, you may find mindfulness and breathwork helpful. Slow, deep breathing such as box breathing can help to calm your ‘fight or flight’ response.²² You could also try listening to a guided meditation to help you feel calmer or drift off to sleep. The NHS has some available, or you can download a free app like Headspace or Calm.

Keep up with hobbies

It can be easy to drop your hobbies when life gets stressful. But it's crucial to have time exclusively for you and things you enjoy. If your circumstances have changed and you can't do the hobbies you used to enjoy, see if there's anything new you can have a go at such as:

• book clubs

• running clubs

• craft groups

• dog walking groups

• ‘speed friending’ events

• choirs and music groups

• gardening groups

• volunteering opportunities

Take time to unplug

Hands up if you've scrolled on your phone to unwind, only for it to make you more anxious? Upsetting news stories or even messages from friends can be overwhelming after a stressful day. If your screen time's looking a little high, take time to 'unplug' from the digital world and try focusing on other things. Try taking an hour or two alone to listen to calming music, go for a walk, do something creative like drawing or baking or spend time with a pet. Limiting technology before bed may also help you drift off more easily and get better-quality sleep, which may help you manage stress.²³

You should talk to your GP about stress if: ^18,24

• it's affecting your daily life (like eating, sleeping, working or seeing friends and family)

• you're struggling to cope

• the strategies you’ve tried aren’t helping

You can bring a friend or family member for support if you'd like. While your GP might not be able to get rid of the source of your stress, they can provide options to help you manage it.

Stress isn't always avoidable, but you don't have to simply put up with how it makes you feel. Paying attention to changes in sleep, mood, memory, concentration or energy can help us recognise when our minds need more care. Small, consistent steps – from making time to unwind and move your body to prioritising sleep – can support brain health and resilience.

Which small change could you make today to give your brain a little more breathing room? Learn the small shifts that could help with burnout or discover the key nutrients for brain health...

Disclaimer – This article provides informational advice and is not a substitute for medical care. Working with experts for accuracy, we take great care to ensure the information is up-to-date and relevant. However, you should always consult your GP or healthcare professional before using supplements or alternative products, particularly if you have medical conditions or are under supervision.