'Brain fog' is a vague, colloquial term for when you feel scatter-brained and mentally impaired.


The term crops up a lot in the medical research literature where it’s used to capture the experiences of cognitive (i.e., mental) difficulties described by various patient groups, from people with chronic fatigue syndrome to patients undergoing chemotherapy (for whom it’s sometimes dubbed ‘chemobrain’) to women transitioning to the menopause.

Recently, as you have likely heard, COVID-19 has also been COVID-19 has also been blamed for causing brain fog, including in the context of long COVID after the initial infection has actually passed.

So if you've ever felt muggy headed, as if you can't concentrate of focus – perhaps you've been forgetful and accident-prone too – then perhaps you've experienced brain fog.

What causes brain fog?

Because 'brain fog' is such a catch-all term, it follows that there can be countless possible causes. For instance, there is speculation that the SARS-CoV-2 virus that causes COVID-19 might reach the brain and directly interfere with brain function.

Similarly, there is tentative evidence that the drugs used in chemotherapy might also have a direct, detrimental physical effect on the brain, thus contributing to brain fog. To take the context of the menopause, it's possible that hormonal changes might directly affect brain function.

However, in all these contexts and others, it's also possible that there are emotional and social contributors to brain fog. For instance, it's telling that many people who have not been infected by coronavirus have nonetheless reported feeling more tired and distracted than usual during the pandemic, perhaps because of the stress and demands of lockdowns and homeworking.

Likewise, one of the main causes of chemobrain is thought to be the stress involved in coping with the illness and treatment. When it comes to the menopause too, there could be indirect contributors to brain fog, such as the effects of poor sleep or the general stresses of navigating a challenging phase of life.

In some situations, such as during pregnancy, the causes of brain fog could even be the mere expectation of mental impairment, fuelled by popular beliefs, rather than there being any underlying direct harmful effect of pregnancy on the brain, or indeed any objective impairment to cognitive function. In this sense, brain fog can be caused by a nocebo effect (a negative placebo effect).

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How to get rid of brain fog

Where the causes of brain fog are due to direct, physically harmful influences on the brain, some of the most effective ways to cope will be compensatory, such as using digital reminders to help support your memory, or making greater use than normal of lists and other planning aids.

If you believe your brain fog might have more psychological or circumstantial causes – perhaps you've been feeling chronically overloaded by having to juggle work responsibilities with parenting, for instance – it might help to making an extra effort to impose some structure on your life, so that you're not constantly multi-tasking. Focusing on one challenge or responsibility at a time will help to clear the fog.

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Similarly, basic lifestyle changes can improve your mental alertness, such as avoiding too much alcohol and fast food; practising good sleep hygiene (try to establish a regular bedtime routine and avoid working or drinking caffeine too late in the evening); and carving out sufficient time to relax and unwind – even a quick nap could help clear your mind.

As a general rule, when we're in a better mood, our mental performance tends to improve, in part due to feeling more energised and motivated. One implication of that is that anything you can do to improve your mood will likely have knock on benefits for your mental alertness, from meeting a friend for a chat to taking a walk in the countryside.

Indeed, exercise is a well-known mood-booster – aim for a moderate intensity that is fun but not overly arduous. Running, in particular, is fantastic way to optimise your mental function and clear the fog. Martial artists too show heightened cognitive function compared with controls.

Find what works for you, but any activity that you enjoy and that gets your heart pumping is likely to help clear that fuzzy-headed feeling.

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Dr Christian Jarrett is a cognitive neuroscientist, science writer and author. He is the Deputy Editor of Psyche, the sister magazine to Aeon that illuminates the human condition through psychology, philosophy and the arts. Jarrett also created the British Psychological Society's Research Digest blog and was the first ever staff journalist on the Society's magazine, The Psychologist. He is author of Great Myths of The Brain and Be Who You Want: Unlocking the Science of Personality Change.