Have you ever walked into a room to fetch something, then forgotten what it was? Or perhaps you’ve been in the middle of a sentence, then lost your train of thought? You might have experienced your mind wandering while trying to concentrate on a presentation at work, or felt a lack of clarity during a mentally intensive task.
Brain fog is an extremely relatable experience – and although it’s often linked with certain conditions or periods of life, it happens to almost everyone from time to time. Normal elements of the human experience such as stress, fatigue, sleep loss or mental overload can all contribute to that feeling that you’re not quite firing on all cylinders. So why does brain fog happen, and what can you do about it?
What’s going on?
According to the NHS, brain fog is a non-medical term used to describe a range of symptoms such as poor concentration, feeling confused or forgetful, thinking more slowly than usual, losing your words or experiencing mental fatigue. Some people describe it as feeling fuzzy, sluggish or not switched on. It can feel similar to the effects of sleep deprivation or stress, but it’s not the same as dementia because it doesn’t involve structural damage to the brain. Brain fog is normal because the human brain doesn’t function as a machine or computer with two settings – on or off. Instead, most people experience natural variations in their cognitive state.
Cendri Hutcherson is an associate professor in the department of psychology at the University of Toronto Scarborough, Canada, and lead author of a 2026 study into day-to-day fluctuations in mental sharpness. She describes cognitive fluctuations as being a bit like adjusting the reception of a radio or quality of image on a television screen.
‘Some days you might see the picture in sharp, high definition, and other days it might be grainy or interrupted by static,’ she says. Mental sharpness can have an impact on all kinds of things as you go about your day-to-day life, including your response to different situations and decision making, as well as overall productivity.
Universal experience
Brain fog is often linked to certain medical conditions, life stages such as menopause or dismissed as tiredness, but in reality it can be common through all stages of life. From students under exam pressure to sleep-deprived new parents, stressed-out executives to jet-lagged travellers, anyone can experience it. Cendri points out that across every demographic, even the most conscientious, goal-driven and determined people experience fluctuations in their mental sharpness and ‘have their bad days’. She says: ‘As far as we can tell, it’s probably a pretty universal experience.’
Cendri also points to the fast pace of modern society and the drain it can have on people’s mental resources. ‘I feel like the pace at which our society operates now is making it more likely that you have a lot of static,’ she says, returning to the analogy of tuning a radio. ‘We are drawn in 50 different directions, which I think does have a long-term effect on clarity.’
Brain fog can be caused by anything that has an impact on the way your brain is able to function. Many of these causes are temporary, such as a bad night’s sleep, dehydration, pressure at work or short illnesses like a stuffy head cold, allergies or infection. Even things like too much screen time can dull mental sharpness. Women can experience brain fog due to hormonal changes as part of their monthly cycle, pregnancy or menopause. People struggling with mental health problems such as depression, stress or burnout can experience brain fog. It can also be a side-effect of medications or a symptom of more serious health issues such as long Covid, strokes, autoimmune conditions, head injuries and cancer. And cognitive decline can be part of the ageing process.
Interestingly, Cendri and her team also found that those involved in their study experienced lower mental sharpness at weekends, indicating that the body’s natural circadian rhythms and habits can play a part. ‘We definitely see that mental sharpness declines from morning to evening,’ she adds. ‘A single day’s hard work did not really reduce mental sharpness the next day, but we did find that a full week of grinding, day after day after day, did start to have effects.’
Pacing yourself
When brain fog strikes it’s often a sign that you need to slow down or rest – but if you’re in the middle of a busy working day, or have non-negotiable commitments, that can be easier said than done. You can take steps to support yourself, though. If focusing is difficult, consider removing any unnecessary distractions for a short time, such as closing your email inbox or setting aside your phone. If your memory doesn’t feel sharp, set reminder alarms, write important information down, make lists or use post-it notes.
Cendri suggests that an awareness of your own mental sharpness fluctuations can help you make decisions on what to prioritise that day – perhaps tackling more demanding tasks on sharper days and saving ‘easy stuff’ for foggier days – rather than ‘putting in more hours to compensate’.
Finding clarity
When it comes to remaining mentally sharp throughout the day, Cendri suggests that variety may have a part to play – alternating activities rather than spending hours doing one task, and building in breaks and changes of scenery. ‘It might just be getting out and going for a walk,’ she says. ‘Doing different things in your day.’ And variety can look different for different people, she adds. ‘For some people it might just be switching from working at a screen to reading a book,’ she says. ‘For others it might be going out and playing soccer. Being a very careful observer of yourself, and what works for you, is better than trying to follow what works for others.’
In the longer term, lifestyle tweaks might help to reduce brain fog, such as a calmer bedtime routine, improvements to your diet and hydration, stress-reduction techniques and spending more time outdoors. If you’ve been struggling with brain fog for a prolonged period, feel it isn’t improving or it’s affecting your day-to-day life, it’s important to speak to your GP to make sure it’s not linked to other health concerns. But for many people brain fog is simply a transient and normal part of the human experience. Cendri concludes that it’s important to be forgiving on those days when you’re feeling a little foggier or fuzzier than usual. ‘Sometimes it’s just not your day – and that’s okay,’ she says. ‘Maybe that’s the day you give yourself a little slack.’
When the fog rolls in
Some practical ways to manage and mitigate brain fog
Drink a glass of water
The brain is about 73 per cent water, so even mild dehydration can affect cognitive performance.
Step outside
Just a short walk outdoors can boost energy levels, reset focus and improve attention, as well as lowering stress and symptoms of depression.
Eat a well-balanced snack
Good nutrition provides a steady supply of glucose for mental energy, reduces inflammation and supports the gut-brain connection.
Try meditation
A short meditation or breathing exercise can be a simple way to lower stress, help you organise your thoughts and reduce mental overstimulation.
Break tasks into bite-sized chunks
Taking breaks before you become severely mentally fatigued can give your brain time to process information and reset.
Take notes
Using lists or a notetaking app can help to lighten your mental load. Try brainstorming exercises or pin boards when working on bigger projects.
Try micro-movements
Standing and stretching, or practising yoga or tai-chi movements, can boost mental alertness.
Brain fog is usually temporary and can be a sign you need to slow down or rest. If you experience brain fog for longer than a few weeks or it’s interfering with your quality of life, it’s important to speak to your GP
For more information on Cendri’s work visit decisionneurolab.com