What is Brain Fog & Mental Fatigue? How to get rid of it?

If you’ve ever experienced a lot of mental fuzziness, daylong drowsiness, and lack of clarity in thinking, you may have brain fog. It can be a symptom of underlying mental fatigue, covid, or deficiencies. Fortunately, there are ways to reduce brain fog and regain mental clarity.

What is brain fog and mental fatigue?

Brain fog^[1] is a mental state characterized by slow thinking, confusion, low alertness, haziness, and difficulty in processing information (collectively known as cognitive difficulties). It is a causal term^[2] describing cognitive difficulties (or sluggish brain function) that often occurs due to a lack of blood flow to the brain and stress. Patients with chronic fatigue syndrome commonly complain about brain fog. People say they have brain fog or a foggy mind when they feel they can’t concentrate and their working memory capacity has dropped for a prolonged period. Brain fog is a major cognitive problem that affects the quality of life.

Mental fatigue is a physical and psychological state of fatigue and exhaustion described as low energy levels, poor cognitive activity, low motivation, and low behavioral activity. It may or may not cause brain fog right away. Mental fatigue that lasts over 6 months is called chronic fatigue syndrome (CFS). People with CFS often experience brain fog as a result.

Why is brain fog bad?

Brain fog can make daily functioning difficult and can even be disabling in a personal, social, and professional context. Apart from the basic cognitive impairment associated with brain fog, its primary cause, which is typically fatigue or an immune or inflammatory issue, can create additional problems. Brain fog makes communication hard and interferes with tasks, which can lead to other problems like demotivation and lack of confidence.

Common signs and symptoms of brain fog

Brain fog most commonly occurs as cognitive impairment and mental fatigue occurs as cognitive, motivational, and physical impairment. Brain fog can range in severity from mild to severe problems in cognitive processes (attention, perception, memory, decision-making, etc.). The most common signs of brain fog are difficulties in our ability to remember, think, and pay attention.

Detailed psychological tests show brain fog coming from CFS impairs^[3] a range of cognitive processes like attention, reaction time, processing speed, and memory. Some patients^[4] also describe their foggy mind as a disoriented state of mind.

Secondary consequences of brain fog

Apart from brain fog disrupting basic cognitive activity, it can create second-order problems like lack of confidence and performance anxiety.

1. Reduced skill and confidence

One study^[5] shows that mental fatigue, which is almost always associated with cognitive impairment, reduces a person’s “action-monitoring” and “response preparedness.” Brain fog can cause the brain to have lesser “error-related negativity” which is our brain’s default response to making errors. This means brain fog can lead to more behavioral and thinking errors that go unchecked. Action-monitoring is how we pay attention to the process of doing some task, and mental fatigue reduces how well we monitor errors and mistakes. Response preparedness also worsens with mental fatigue, making us feel less prepared to perform any activity. This is why brain fog which is perceived as mental fatigue can hamper performance, lead to more mistakes in simple tasks, and lower confidence in performing any task.

2. Low motivation and high procrastination

Mental fatigue, according to some theorists^[6], occurs when the energy cost of doing a task outweighs the anticipated reward of doing that task. If the cost of doing an activity is low and the reward is high, they will perform the task. This theory explains why people experiencing mental fatigue find it difficult to do simple tasks and lose motivation – they often feel that doing the task is a burden and will take a toll on them. Sometimes, an exaggerated perception of how costly or effort-demanding a task is can lower motivation in those with brain fog. In many contexts, this is equal to procrastination – the task is considered emotionally heavy because of possible negative consequences or perceived difficulty and we then avoid it to do something more fun and easy.

What causes brain fog?

Brain fog can be a symptom of many medical, lifestyle, and psychological factors. In some of these findings, researchers have used tests made to identify brain fog. In others, research shows symptoms that are commonly interpreted as brain fog.

1. Chronic fatigue syndrome (CFS): CFS is a consistent state of physical and mental fatigue^[7]. One study^[8] suggests mental fatigue in CFS is a more exaggerated perception of fatigue than true muscular fatigue after physical exertion.
2. Long COVID: Long-lasting lingering symptoms from the novel coronavirus infection can include cell damage and cognitive impairments^[9] possibly caused by a lack of oxygen to the brain. The coronavirus may also disrupt neural cell functioning by disrupting the mitochondria (it’s no longer the powerhouse of the cell) after the viral DNA integrates into the nervous system. Some researchers suggest COVID-19 brain fog^[10] is similar to covid-induced Alzheimer’s disease because of similar damage to the structure of the brain.
3. Withdrawal symptoms: Medical drugs such as antidepressants can create withdrawal symptoms if they aren’t planned appropriately. According to a study^[11], a commonly reported withdrawal symptom is brain fog – about 25% of those who experience antidepressant withdrawals are likely to experience low concentration. Alcohol withdrawal^[12] and nicotine withdrawal^[13] can cause confusion, fogginess, and poor attention. Cognitive deficits caused by withdrawal may motivate people to smoke again to reduce the symptoms. This may increase dependence on substances for productivity and change one’s beliefs about what causes brain fog. They may even rationalize excessive consumption with self-talk like, “I need caffeine/cigarettes/alcohol to function at my best.”
4. Gastrointestinal problems: Stomach and intestine problems like unhealthy gut biome, gas, and bloating may have an effect on brain functioning. Preliminary^[14] but inconclusive research^[15] suggests excessive probiotic use may lead to the overgrowth of bacteria in the small intestine and that might lead to brain fog. The mechanisms of how the gut biome affects cognition are still being explored, but a promising connection^[16] is that the gut biome sends signals to the brain that guide myelination (fatty layers on neurons that improve neural signals), regulate gene expression, synthesize neurotransmitters, improve microglia functioning (microglia are the brain’s support staff) and reduce inflammation.
5. Dehydration: Dehydration through reduced water intake or excessive fluid loss due to disease can disrupt brain function and core cognitive processing resulting in brain fog. Blood carries water, oxygen, nutrients, glucose, hormones/neurotransmitters, and metabolites that keep the brain functioning. Reduced water in the body affects blood supply to the brain.
6. Headaches/Migraines: Headaches are different types of pain caused by inflammation, blood flow problems, and irregular nerve signals in the brain. They are caused by different diseases or events like a stroke, acute stress, or a hangover. People with headaches or migraines show brain fog like symptoms^[17] such as low verbal memory, slow processing speed, poor attention, and poor decision-making during the pain. But the dysfunction doesn’t appear to create a permanent state of brain fog or slow cognitive decline.
7. Postural orthostatic tachycardia syndrome: Reduced blood flow to the brain after getting up too fast^[18] after lying down. People may regularly experience short-term brain fog after getting out of bed too quickly/jerkily. It’s commonly called a headrush and anecdotal evidence suggest dehydration makes it worse.
8. Myalgic Encephalomyelitis: A neurological and immune dysfunction^[19] characterized by cognitive impairments, changes in blood flow, and prolonged and excess fatigue after minor exertion.
9. Primary immunodeficiency disease (PID): People with PID have immune system malfunction which increases the risk of infection and autoimmune problems like flare-ups. A survey^[20] suggests people with PID experience memory dysfunction or at least perceive they have memory dysfunction.
10. Multiple Sclerosis (MS): MS is a progressively worsening condition caused by the deterioration of fatty layers on nerves (called the myelin sheath). The myelin sheath improves nerve “signal” efficiency in healthy brains. De-myelination worsens brain-body coordination and vision, and creates fatigue. About half the people^[21] with MS have cognitive impairments due to large structural changes in the brain.
11. Lupus: Lupus^[22] is an autoimmune disease where the system unnecessarily attacks healthy tissue with symptoms like rashes, joint pain, fever, and organ damage. It affects the brain, heart, lungs, joints, kidneys, and skin tissue with inflammation and flare-ups. Inflammation causes brain fog in many lupus patients. One mechanism for this is inflammation disrupts long-term potentiation – the process of strengthening a neural connection which makes neural signals more efficient.
12. Brain inflammation: Inefficient glucose supply to the brain, low nutrients, and poor energy management between neurons can create an inflammatory response in the brain^[23]. During inflammation, the first defense against infection, irritation, or foreign body invasion, immune cells invade the brain to nullify the problem. But sometimes, the cells attack healthy cells which causes problems. Then, the brain’s functioning is threatened and creates an overactive recovery response that disrupts normal cognitive functioning. Brain inflammation, according to a study on rats^[24], can reduce the growth of efficient neural networks (called neurogenesis) which is necessary for optimal cognitive functioning.
13. Stress: When our ability to perform a task needs more energy than we have, we may show overt symptoms like procrastination and an aversion to performing cognitive tasks that demand a high cognitive load (high mental effort).
14. Depression: Depression is a general state of low motivation, low energy, negative thoughts, lack of positive emotions, and limited mental functioning. Depression goes hand-in-hand with cognitive impairment which can be interpreted as a foggy mind with inattention being a core symptom^[25].
15. Anxiety: Anxiety is a revved-up mental and physical state that puts the body in survival mode which generates unwanted negative thoughts to act on safety, feel in control, and ward off threats. It affects how we pay attention and also changes mental processing to highlight threatening and safety-oriented information and clouds the perception of non-threatening information. Introspectively, one may describe the overall experience as a fatigued mind.
16. Low dietary nutrition: An imbalanced diet with low vitamins, minerals, flavonoids, and fatty acids and high processed sugar through carbs and aerated drinks can impair cognitive function. Low choline^[26], a precursor chemical for the neurotransmitter acetylcholine that governs cognition, can create mental fatigue and associated cognitive dysfunction. It is found in meats, dairy, nuts, legumes, eggs, whole grains, apples, tangerine, kiwi, broccoli, and beans.^[27]
17. Hypothyroidism: Hypothyroidism is a condition where the thyroid gland doesn’t create and release enough thyroid hormone^[28] into the bloodstream. It typically reduces metabolism and causes obesity, lethargy, and brain fog. Studies suggest it is unclear if brain fog in hypothyroidism is a symptom or a side effect of high-dose LT4 treatment (standard treatment drug called levothyroxine).
18. Obesity: An abnormally high proportion of fat in the body (BMI > 25) and below-average metabolism can introduce chronic fatigue and inflammation. A consequence of that is brain fog and low self-efficacy (confidence in one’s capacity to perform) that starts a cascade of lifestyle and medical problems that eventually worsen brain fog.
19. Cancer treatment: Chemotherapy^[29] is a treatment for multiple types of cancers that involves using radiation to destroy tumors. It sometimes causes toxicity in the nervous system leading to widespread cognitive deficits and haziness (aka chemobrain). One theory is that chemotherapy causes irregular changes in gene expression (how genes manifest into biological instructions) in the hippocampus and prefrontal cortex. Both brain regions are responsible for long-term memory, working memory, and executive functions like decision-making.
20. Sleep deprivation: Regular insufficient sleep, usually under 7 hours for those younger than 60 years of age, causes a host of cognitive impairments. Sleep disruptions cause many different cognitive difficulties like poor attention, biased attention, overreaction, decision-fatigue, memory loss, confusion, slow processing speed, and slow reaction time.
21. Celiac disease and gluten sensitivity: Celiac disease,^[30] an immune reaction in the small intestine caused by gluten, can create cognitive symptoms that resemble brain fog. Gluten is a naturally occurring protein found in grains like wheat, rye, and barley. Non-celiac-gluten-sensitivity can also cause brain fog. Researchers propose that higher levels of cytokines in the system and low serotonin in the brain explain brain fog.
22. Parkinson’s disease (PD): PD is a neurodegenerative disorder^[31] in older people that affects movement, creates stiffness, tremors, and loss of control. It is typically caused by degenerating neurons in the substantia nigra – a brain region that creates dopamine which acts as a messenger chemical between the brain and body to guide muscle movement. One possible mechanism^[32] is that important DNA inside the mitochondria is deleted (reasons unclear), leading to nerve loss in the substantia nigra. Patients with PD often have cognitive difficulties like confusion and speech production.
23. Alzheimer’s disease (AD): AD is a brain disease^[33] that degenerates neural connections resulting in memory loss and an overall drop in mental functioning. Fogginess is a common complaint in patients with worsening dementia (an umbrella term for poor judgment, reasoning, memory, and attention) caused by AD.
24. Fibromyalgia: Fibromyalgia is widespread pain and tenderness in muscles with additional fatigue, disturbed sleep and mood, along with cognitive dysfunction like forgetfulness, and low alertness. Brain fog (aka fibro fog in this case^[34]) is a subjective and clinically significant aspect of living with fibromyalgia.
25. Passive lifestyle & low physical activity: A lack of physical and mental engagement in day-to-day life causes boredom, lethargy, shallow emotional experiences, and low metabolism. This, in turn, affects overall cognitive make-up and motivation in the near future. It may become chronic over time.
26. Excessive alcohol, drug, toxin intake: Toxicity in the central nervous system due to excess intake of drugs and alcohol^[35] impairs memory and attention, causes frequent hangovers, blackouts and nutritional deficiencies, and causes chemical changes in the brain that induce fatigue. Excessive alcohol^[36] can cause abnormal activity in the hippocampus (responsible for memory).
27. Head injury and concussions: Physical blows to the head can disturb the brain’s structural integrity causing various impairments. A study^[37] on athletes with concussions suggests 1 in 6 have some degree of fogginess with slower reaction times, reduced memory, and slower processing speed a week after injury.

A similar and related problem

Sluggish cognitive tempo (SCT): Some people, particularly children & younger adults, may exhibit “sluggish cognitive tempo” which resembles ADHD but isn’t a diagnosable problem^[38]. They may interpret their SCT as a “permanent brain fog”. Sluggish cognitive tempo is a collection of symptoms like slow behavior/thinking, low concentration/alertness, and frequent mind-wandering/daydreaming. On the outside, this looks like people with SCT are absent-minded and slow to react or act. A study suggests sluggish cognitive^[39] tempo occurs when the brain’s “inhibitory system” (the ability to stop a thought) is too active and memory systems are slow. An overactive inhibitory system means the brain stops (inhibits) a thought too early to fully convert it into behavior. A slow memory system means it takes time for the brain to “collect” and “rearrange” its resources, which delays thoughts, behavior, and final response times. It often leads to daydreaming (continuous changing of incomplete thoughts), slow behavior, delayed verbal responses, and slow understanding/comprehension (due to a lack of focus).

How can you get rid of brain fog?

1. Get in touch with nature: Connecting with nature by exposing yourself to greenery and animals is a great way to maintain brain health and reduce brain fog. Natural events like waterfalls and phytoncides given out by trees make us feel good and improve our immune system (which counters inflammation type causes of brain fog). Inhaling Mycobacterium vaccae, which is found in water, soil, and vegetation, can improve brain function by making neurotransmitters like GABA and acetylcholine which are important for cognition. Microorganisms and organic compounds found in forests are also anti-inflammatory.
2. Rehydrate: Water is essential for baseline biological functioning as it carries the oxygen required by the brain. Staying hydrated is mandatory for even average cognitive performance. In fact, dehydration is a major reason people lose productivity and concentration while studying. Drinking water can boost attention, fine motor control^[40], exam grades, and memory.
3. Manage overall stress: Chronic stress or severe acute stress can create long-lasting or short-term brain fog. So relaxation and self-care-oriented activities can help you recover from fogginess or fatigue in many situations. Moreover, having fun improves baseline cognitive abilities. Still, some level of stress, which can be interpreted as feeling “challenged,” can keep the brain engaged and motivated. A little bit of challenge can help you reach the flow state where you feel one with a task. Which, in a way, is the opposite of having brain fog.
4. Improve sleep hygiene: Sleep hygiene includes your activities before and after sleep, room and body temperature, and quality of sleep using blankets, pillows, or accessories like eye patches. Sleep serves the function of biological maintenance, cognitive reorganization, and emotional regulation. All 3 affect the severity of many diseases, speed of healing, and mental functioning. Effectively, good sleep can defend against brain fog and improve your chances of recovery.
5. Have a change of routine and do refreshing, enjoyable activities: Routines are like habits that operate on an automatic level without much thought. To liven up a cognitively dull state like fatigue or fogginess, you can make deliberate changes in your everyday routine. Mindfulness is one way to start being more cognitive. Similarly, changing routines and daily behaviors force the brain to re-engage with the world in novel ways that can clear up the fog because the brain has to necessarily adapt to new circumstances, which requires mental clarity. Relaxing and enjoying your time creates the opportunity to snap out of fogginess due to the nature of positive emotions – they force a change in how you interpret and focus on the world.
6. Modify diet in a way that improves cognitive functioning
   1. Increase Choline: Choline is a precursor molecule that builds acetylcholine which is needed for normal cognitive functioning. Choline is found in meats, dairy, nuts, legumes, eggs, whole grains, apples, tangerine, kiwi, broccoli, and beans.^[41]
   2. Reduce gluten: Since gluten sensitivity and intolerance are a primary cause of brain fog, avoiding or reducing gluten can help regain mental clarity and reduce fatigue. Avoid gluten which is present in many types of bread.
   3. Enter ketosis: People who do a prolonged fast (more than 48 hours) report an increase in cognitive ability^[42]. Their brain fog vanishes. They feel alert with reduced fatigue and increased focus. When a person fasts for more than 2-4 days, their body doesn’t have enough carbs to burn for energy. Instead, it starts using stored fat for energy which produces “ketones” in a process called ketosis. Prolonged fasting should be a medically informed decision because there may be complications in the case of diabetes or pregnancy.
   4. Eat a diet that promotes cognitive well-being:
      1. Consume plants, grains, and fruits.
      2. Try including soya and fiber.
      3. Consume omega-3 fatty acids.
      4. Rectify vitamin and mineral deficiencies (particularly folic acid, vitamin B12, and vitamin D)
      5. Avoid excess sugars, fats, and carbs.
7. Explore underlying diseases and dysfunction: Many diseases (listed above) can cause chronic fatigue and brain fog. Ruling out diseases as a cause is a first step toward recovering from brain fog. Some of the common diseases or situations that lead to brain fog or chronic fatigue are COVID-19, gluten sensitivity, substance withdrawal, chronic stress/fatigue, depression, anxiety, lack of exposure to nature, passive lifestyle, and medical treatments.
8. Use music to re-engage the brain in new ways: Music engages many different parts of the brain in novel ways and it typically regulates cognitive resources and mood. Typically, people feel re-energized, clarity, and disconnected from previous sluggishness by listening to music.
9. Increase physical exercise and deliberate movement: All forms of moderate exercise^[43] and movement-based therapies^[44] like dance, drama, nature therapy, and adventure sports can counter brain fog by increasing blood flow to the brain and countering brain inflammation. Dance therapy is particularly helpful^[45] in countering old-age-related cognitive impairment.
10. Undergo cognitive rehabilitation and take on physical and mental challenges: Cognitive rehabilitation is systematically working on cognitive functions like attention, thinking, and memory by doing increasingly difficult tasks, games, activities, hobbies, and puzzles. Activities that engage core cognitive functions can keep the brain healthy and buffer against cognitive decline and brain fog. Purposeful learning promotes synaptic plasticity (the brain’s ability to rewire itself) and it utilizes neurogenesis (the pre-programmed growth of new neurons). Both processes use and improve cognition to reduce fatigue by (figuratively) shaking up the brain.
11. Promote BDNF: BDNF (brain-derived neurotrophic factor^[46]) is a protein available in the brain which is responsible for neural growth and cell survival. Certain energetic lifestyle habits^[47] like regular exercise and a healthy diet can promote BDNF which helps to improve long-term cognitive wellbeing. A passive lifestyle with no movement (too much sitting, no exercise) and high stress can decrease BDNF resulting in poorer brain health.

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