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Do you ever feel like your brain isn’t working as it should—like you’re walking around in a mental fog? You’re not alone. Brain fog, a term used for sluggish thinking, forgetfulness, and lack of focus, affects people for countless reasons. However, brain fog is rarely talked about in your doctor's office-- with the attention on memory loss instead. What's more, information you find online can often be incomplete at best and flat-out wrong at worst. But we've got good news, while the triggers behind brain fog can be complicated, the solutions are easier than you might think.
Key Takeaways
Brain fog is frequently linked to inflammation caused by conditions like autoimmune diseases, chronic fatigue syndrome, and obesity.
Fluctuations in hormones during pregnancy, menopause, or due to conditions like hypothyroidism or low testosterone can impair cognitive function.
Better sleep, exercise, stress relief, and a nutrient-rich diet are effective ways to reduce brain fog and enhance mental clarity.
What is Brain Fog?
You won’t find brain fog listed in a medical dictionary because it’s not a medical condition as such. Rather, the phrase is used to describe a constellation of symptoms that give rise to sluggish cognition.
The history of brain fog goes back almost two centuries, when it was used to describe the mental exhaustion experienced by “brainworkers” like lawyers and teachers. But the phrase only came into its own in the 1990s when it was linked with chronic fatigue syndrome (CFS), also known as Myalgic Encephalomyelitis (ME), and autoimmune disorders that were being highlighted at that time.
Since then, scientists have been asking "what causes fogginess?" And they've uncovered more questions than answers. For one thing, they've learned that brain fog is caused by a lot more than autoimmune illnesses. From poor sleep and anxiety to viral infections like COVID-19 and chemo-brain, brain fog can result from numerous physical and mental challenges.
It’s not always easy for patients to describe their cognitive fog, they just know their brains aren’t working as they should be. Interestingly, and what’s baffling, is they may still perform well on cognitive tests, not appearing to have any cognitive impairment at all! 1
Brain fog symptoms patients describe include:
Inability to focus, concentrate, or pay attention
Forgetfulness
Confusion or feeling spaced out
Difficulty processing information
Hard to multitask
Mental sluggishness or exhaustion
Losing train of thought
Unable to find the right words
People can suffer from a foggy brain for multiple reasons. Finding the root cause can require detective work worthy of Sherlock Holmes as there are plenty of places to look including lifestyle, diet, nutritional deficiencies, hormonal factors, medical conditions and medications.
Let’s start with...
Brain Fog Cause: Medical Conditions Stoking Inflammation
Many common medical conditions can significantly impact cognitive function by disrupting normal brain chemistry and inflammation levels. In fact, inflammatory molecules secreted in the brain are linked to many medical conditions and are thought to be an underlying cause of brain fog. 2 These conditions include:
Migraine: Sufferers commonly report their concentration and memory can be impacted prior to, during, and after a migraine attack.
Autoimmune diseases: Some autoimmune diseases such as lupus, Crohn’s disease, celiac and rheumatoid arthritis involve inflammation throughout the body, leading to brain fog symptoms. Others, like multiple sclerosis directly affect the brain and central nervous system by its erosion of the myelin sheath that surrounds nerves. This slows or stops transmission of electrical impulses causing a range of neurological symptoms including brain fog.
Fibromyalgia: As well as causing pain throughout the body, this condition also affects concentration, thinking, and memory. This has been dubbed fibro fog. Changes to signaling pathways in the brain that transmit pain impulses are believed to contribute to the patients’ fogginess.
Chronic Fatigue Syndrome (CFS)/Myalgic Encephalomyelitis(ME): Brain fog is a feature of this condition with symptoms fluctuating and varying from mild to severe. Cognitive and physical fatigue lasts for at least six months and can continue for years.
Inflammatory Infections: If the brain becomes a target for infections it can lead to cognitive problems. These include Lyme disease, exposure to mold, West Nile virus and COVID-19. Infections like these are one of the reasons for brain fog.
In fact, almost one in five people who had COVID don’t shake it off within a few weeks and develop Long COVID. In these patients, certain types of immune cells are thought to be activated in the brain. This leads patients to commonly complain of “muddled or fuzzy thoughts”. Research shows that conditions like long COVID can reduce brain processing speed by up to 30%.
Mood disorders: Raised levels of inflammatory markers in the brain are found in people diagnosed with anxiety and there’s evidence that some people with depression also have brain inflammation. This may be why these disorders can affect people’s ability to think and remember.
Obesity: This can lead to inflammation all over the body including the brain which may be why obese people often report brain fog.
Seasonal Allergies: Many experience brain fog during the allergy season. The body responds to those affected by producing histamines and proteins called cytokines which results in inflammation.
Hormonal Factors Leading to Brain Fog
Brain functioning can be affected by changes – either up or down - in hormone levels. During pregnancy, estrogen and progesterone are elevated and this can affect cognition. Four out of five pregnant women report “baby brain” with forgetfulness being the most reported problem among many others including poor attention and concentration.
At menopause it’s a repeat performance except this time estrogen levels drop giving rise to poor concentration, memory problems and woolly thinking. In fact, hormonal changes during menopause can temporarily decrease memory function by 15-20%.
Men don’t escape either as low testosterone levels can cause difficulties in thinking clearly.
One common medical condition that can cause brain fog is hypothyroidism. A drop in thyroid hormone can lead to increased forgetfulness, ability to find the right word and slow thinking. These problems are not always resolved with thyroid medication. 3
Brain Fog In Your Medicine Cabinet
Both prescribed and over the counter drugs can cause brain fog by interfering with hormone and neurotransmitter signals in the brain. 4
Medications for the following conditions may cause brain fog:
Insomnia - one of the most common medicinal culprits of brain fog
Pain - most cause confusion and memory issues
Migraine/Seizures - anti-epileptic drugs, which may also be used to prevent migraine attacks
Arthritis - long-term use of corticosteroids
Anxiety and depression - various drugs for these conditions
Allergies - over-the-counter antihistamines
Chemotherapy - many patients report lapses in focus and concentration, difficulty in finishing what they started, visual and verbal memory loss, diminished processing speed and problems learning new skills. After so many patients were asking, "what causes fuzzy brain," researchers gave this phenomenon the name chemo brain.
If you notice brain fog symptoms not long after taking a new medication, this would be a good clue that the drug is to blame. A change in dosage or a different drug may resolve cognitive issues.
Lifestyle Factors Reaping Brain Havoc
Poor sleep
Sleep isn't just a daily timeout – it's your brain's essential maintenance period. During deep sleep, your brain flushes out toxic proteins that build up during waking hours, similar to a nighttime cleaning crew. Research from the National Institutes of Health shows that this "glymphatic system" is up to 10 times more active when we're sleeping, making those seven to nine hours crucial for keeping our mental machinery running smoothly.
The statistics paint a concerning picture of our collective sleep deficit. While seven to nine hours is the sweet spot for optimal brain function, a startling 2022 survey by the American Academy of Sleep Medicine found that 32% of working adults get by on six or fewer hours of sleep. Even more troubling, chronic sleep deprivation has been linked to a 30% reduction in working memory capacity and a 40% decrease in our ability to form new memories.
This helps explain why a poor night's sleep can leave you fumbling for words or struggling to remember where you put your keys. No wonder so many people complain of fuzzy thinking, poor concentration and confusion.
Not enough exercise (Prolonged sedentary time)
When we sit for extended periods, we're not just affecting our bodies – we're literally starving our brains of vital resources. Research from the University of California shows that physical inactivity reduces blood flow to the brain by up to 20-30%, particularly in regions crucial for memory and problem-solving. This reduced circulation means less oxygen and fewer nutrients reaching our brain cells, creating the perfect storm for mental fog and sluggish thinking.
Chronic stress
Stress reduces blood flow to the brain, impacting memory, and leads to mental exhaustion, making it difficult to think clearly.
Nutritional deficiencies and trigger foods
If the brain isn’t provided with the raw materials it needs to function, it will let you down in many ways, one of which is the ability to think clearly, focus and recall information.
Ultraprocessed foods high in unhealthy fats and sugars and poor in essential nutrients lead to brain inflammation and a brain that doesn’t work as well at is should. Dehydration also impacts the ability to use our brain as can drinking too much alcohol and caffeinated drinks. People with food allergies or sensitivities can also develop brain fog if they eat an offending food.
Resolving Brain Fog
Not all cases of brain fog can be resolved easily if they are a feature of an incurable medical condition, or a medication required for disease control, but for anything else there are strategies we can adopt to clear away the mental fog. 5
As previously mentioned, if brain fog develops after a new medication, then speak to your doctor or pharmacist about a change of dose or an alternative medication. Or avoid medication altogether. For instance, instead of antihistamines for seasonal allergies, try natural options like saline rinsing and nasal balms.
Get a good night’s sleep
The impact of sleep deprivation goes beyond just feeling tired. When we consistently shortchange our sleep, we're actually changing how our brain functions on a cellular level. Studies show that just one night of poor sleep can increase inflammation markers in the brain by up to 20%, disrupting the neural networks responsible for focus, decision-making, and emotional regulation. This explains why sleep-deprived individuals often report feeling like they're thinking through mud – their brain's processing speed quite literally slows down, making every mental task require more effort than usual.As well as aiming for at least 7 hours of sleep, keep a regular sleep schedule. Set up your sleep environment to optimize your chances of sleeping well. This involves keeping the bedroom quiet, dark and cool, keeping electronic devices out of the bedroom and not used for an hour before bedtime, and not eating for at least three hours before retiring.
Sleep disorders such a sleep apnea disrupt sleep, affect cognitive function and can have serious consequences for the whole body, so medical help should be sought.
Get moving
Prolonged sitting is harmful to the brain and overall health even, surprisingly, for those who go the gym each day.
The impact of a sedentary lifestyle on cognitive function is striking. A landmark 2021 study in the Journal of Applied Physiology found that adults who sat for more than 8 hours daily showed a 15% decrease in cognitive performance compared to their more active peers. Even more concerning, researchers at UCLA discovered that sedentary individuals had up to 10% less brain volume in regions associated with memory and attention – suggesting that too much sitting might actually shrink key areas of our brain over time.
As Italian scientists write: physical exercise “induces structural and functional changes in the brain, determining enormous biological, and psychological benefits.” 6
So get moving any way you can. Even a simple activity like walking can make a big difference to how you feel. Breaking up periods of inactivity with movement can have immediate benefits. Studies show that just five minutes of walking every hour can increase brain blood flow by up to 15%, while regular exercise boosts levels of BDNF (Brain-Derived Neurotrophic Factor) – often called "Miracle-Gro for the brain" – by up to 300%. This crucial protein helps create new neural connections and protect existing brain cells, essentially acting as a natural brain fog fighter. The evidence is clear: our brains work better when our bodies move regularly.
Stimulate your brain
Recent research in neuroscience has revealed just how powerful mental challenges can be for brain health. A groundbreaking 2019 study in the International Journal of Geriatric Psychiatry found that adults who regularly engaged in puzzles and board games had cognitive function equivalent to someone 10 years younger, particularly in memory and reasoning tasks. Even more impressive, researchers at the University of Exeter discovered that people who played games like chess or completed crosswords daily showed a 74% reduction in cognitive decline compared to those who rarely exercised their minds with such activities.
The benefits of mental stimulation extend beyond just maintaining cognitive function – they actively enhance it. A study published in the Journal of Neuroscience showed that participants who spent just 15 minutes daily on challenging brain games improved their processing speed by 33% over six weeks. The brain's remarkable plasticity means it responds quickly to mental exercise: participants in a Memory Challenge Study at Harvard Medical School demonstrated a 40% improvement in attention span and a 59% boost in problem-solving abilities after completing daily cognitive training exercises for one month. Think of your brain like a muscle – each puzzle, game, or new learning experience acts like a mental workout, strengthening neural connections and building cognitive reserve.
Chill out
When life is hectic it’s difficult to make time for yourself, but your brain needs a break. Find time for activities you enjoy, meet up with friends, take a daily walk, read a novel, learn meditation or deep breathing techniques.
Deep relaxation techniques like meditation and mindful breathing trigger your body's parasympathetic nervous system, reducing stress hormones like cortisol by up to 50% while increasing blood flow to your brain. This physiological shift helps clear mental cloudiness by allowing your brain to shift from "fight or flight" mode to "rest and digest," where it can process information more efficiently and restore mental clarity.
If needed, explore cognitive behavioral therapy.
Eat more nutritious food
A natural, healthy, nutrient-dense diet is good for the brain and the whole body.
One such diet was developed to support brain health specifically. It’s called the MIND diet. Berries and green leafy vegetables take center stage together with whole grains, other veg, beans, nuts, poultry, fish, olive oil, and wine in moderation.
This diet also counters inflammation. In addition, drink adequate amounts of water and don’t go over the top on alcohol and caffeine.
Support your brain with nutritional supplements
Many essential nutrients play key roles in the brain but are commonly deficient in the diet. For instance, magnesium is needed for healthy psychological and cognitive performance and its deficiency can lead to brain fog.
Yet as a Harvard scientist writes: “its consumption has significantly decreased in the last few decades because of changes in dietary habits; furthermore, removal of magnesium during food processing also contributes to reduced magnesium uptake.” 7
The same story can be told for many other essential nutrients like omega-3s (which can improve cognitive function by up to 26%), vitamin B12 (critical for neural function), and adaptogens like Lion's Mane mushroom (shown to reduce mild cognitive impairment by 30% in clinical trials) can help combat mental cloudiness.
Additionally, natural nootropics like Bacopa monnieri and ginkgo biloba have been clinically proven to enhance memory and mental processing speed, with research showing improvements in cognitive performance of 23% and 38% respectively in controlled studies.
So it’s important to plug nutritional gaps as well as provide additional nutritional support to clear foggy thinking.
Summary
Brain fog describes a sense of mental cloudiness, forgetfulness, and difficulty concentrating. Often linked to inflammation, hormonal changes, medications, or lifestyle factors like poor diet and stress, brain fog can sometimes stem from underlying medical conditions. While resolving brain fog may require medical advice in chronic cases, most people can experience improvement by adopting lifestyle changes such as better sleep, a nutrient-dense diet, regular exercise, and stress management.
Frequently Asked Questions
What is the root cause of brain fog?
It doesn’t have a single root cause as such. It can come about for many reasons ranging from a lack of sleep to a serious medical condition that affects the brain.
What deficiency causes brain fog?
It may or may not be caused by a deficiency. But many nutrients are directly involved with brain health. These include the vitamin B complex, especially B12, vitamin C and vitamin D, and the minerals magnesium and zinc among others.
How do you clear up brain fog?
By working through various strategies. It can range from a change in drug prescription or getting a full night’s sleep to taking up exercise, relieving stress, revamping the diet or taking a brain supporting supplement.
Can brain fog be permanent?
How long it lasts will depend on the underlying cause. For instance, it should resolve after pregnancy, menopause or Long COVID, but may persist with chronic fatigue/ME, and autoimmune diseases. Successful disease management and addressing diet and lifestyle factors will help in most cases.
What foods help clear brain fog?
Foods rich in antioxidants, healthy fats, vitamins, and minerals—like leafy greens, berries, fish, nuts, and seeds—can support brain health and reduce fog.
1 brainHQ Could you have brain fog? How to tell and what to do February 16, 2023
2 Medical News Today Brain fog: Causes and tips March 3, 2023
3 Samuels MH Psychiatric and cognitive manifestations of hypothyroidism Curr Opin Endocrinol Diabetes Obes. 2014 Oct;21(5):377-83
4 Cleveland Clinic Brain Fog 05/14/2024
5 verywell health Brain Fog: What Clears a Cloudy Head Feeling? March 06, 2024
6 Mandolesi L, et al. Effects of Physical Exercise on Cognitive Functioning and Wellbeing: Biological and Psychological Benefits Front Psychol. 2018 Apr 27;9:509
7 Razzaque MS. Magnesium: Are We Consuming Enough? Nutrients. 2018 Dec 2;10(12):1863
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