How to Clear Brain Fog: Effective Strategies

That frustrating mental cloudiness has real causes—and research-backed solutions. Brain fog affects roughly one in four adults, making it difficult to focus, remember simple things, or think clearly. The good news: it's almost always reversible. This guide explains what brain fog actually is, what causes it, and which strategies have the strongest scientific evidence for clearing it.

What is brain fog, exactly?

Brain fog isn't a formal medical diagnosis—it's a term describing a cluster of cognitive symptoms that interfere with daily life. People experiencing brain fog commonly report mental haziness, difficulty concentrating, forgetfulness, slowed thinking, and trouble finding the right words. Research published in Trends in Neurosciences in 2025 defines it as symptoms "implicating cognition (particularly attention, memory, and language), affect, and fatigue."

A large study of nearly 26,000 people found that about 28% reported experiencing brain fog, with difficulty focusing being the most common complaint. The condition spans demographics but is particularly common after COVID-19 infection, during menopause, and in people with chronic conditions like fibromyalgia and chronic fatigue syndrome.

Here's an important distinction: brain fog is not dementia. Brain fog is typically intermittent and reversible, while dementia is progressive and involves irreversible brain changes. If you sometimes forget where you put your keys, that's brain fog territory. If you're holding your keys but can't remember what they're for, that warrants medical evaluation.

Your brain on fog: The neuroscience behind the cloudiness

Understanding what's happening in your brain during foggy episodes helps explain why certain interventions work. Research has identified several interconnected mechanisms at play.

Neuroinflammation sits at the center. When inflammatory molecules called cytokines become elevated—whether from infection, chronic stress, poor sleep, or other triggers—they interfere with brain function. A landmark 2024 study in Nature Neuroscience found that people with brain fog had elevated inflammatory markers and sustained activation of brain immune cells called microglia. These inflammatory signals disrupt synaptic plasticity, the brain's ability to form and strengthen neural connections essential for learning and memory.

The blood-brain barrier can become leaky. This protective shield normally keeps harmful substances in your bloodstream from reaching your brain. The same Nature Neuroscience study used specialized MRI imaging to show that people with brain fog had increased permeability in this barrier, particularly in areas important for memory and executive function. When the barrier becomes compromised, inflammatory molecules that normally stay in the bloodstream can enter brain tissue directly.

Cerebral blood flow often decreases during brain fog episodes. Your brain needs consistent oxygen and glucose delivery to function optimally—anything that impairs this delivery affects mental clarity. Multiple brain imaging studies have documented reduced blood flow to key cognitive regions in people experiencing brain fog.

Neurotransmitter systems get disrupted as well. Inflammation affects the production and function of neurotransmitters like dopamine and serotonin, which regulate attention, motivation, and mood. This explains why brain fog often accompanies mood changes and fatigue.

The root causes: Why brain fog happens

Brain fog is almost always a symptom of something else. Identifying your personal triggers is the first step toward clearing it. Here are the most common causes, organized by strength of evidence.

Sleep problems rank as a primary culprit

The evidence linking poor sleep to cognitive dysfunction is among the strongest in neuroscience. A comprehensive review of sleep deprivation studies found that even short-term sleep deprivation significantly impairs attention, working memory, and processing speed. The effects aren't subtle—researchers documented large effect sizes for attention lapses and moderate impairments in working memory.

Sleep serves essential brain maintenance functions. During deep sleep, your brain's glymphatic system clears metabolic waste products, including proteins associated with neurodegeneration. Sleep deprivation impairs this clearance system, leading to toxic buildup. Research shows that just 24 hours without sleep produces measurable changes in brain wave patterns associated with cognitive decline.

Both sleep quantity and quality matter. Fragmented sleep—even if you're technically in bed for eight hours—doesn't provide the same cognitive benefits as consolidated sleep with proper cycling through sleep stages.

Chronic stress physically changes your brain

When stress becomes chronic, the constant elevation of cortisol—your primary stress hormone—causes measurable brain changes. Studies of people with Cushing's syndrome, a condition causing excessive cortisol, show reduced hippocampal volume and severe memory impairments. The hippocampus is particularly vulnerable to cortisol damage, and it's critical for forming new memories.

The stress response system can become dysregulated with chronic stress, leading to either excessive cortisol production or, eventually, blunted cortisol responses. Both extremes impair cognition. Research shows that cortisol levels follow a U-shaped relationship with cognitive performance: both too low and too high levels impair function.

Chronic stress also triggers neuroinflammation, creating a vicious cycle. Elevated stress hormones increase inflammatory cytokines, which further impair cognitive function and can perpetuate the stress response.

Inflammation from multiple sources affects the brain

Systemic inflammation—whether from illness, autoimmune conditions, obesity, or even a poor diet—impacts brain function. A University of Birmingham study demonstrated that even mild inflammation required participants to exert greater cognitive effort to maintain their normal performance levels.

The gut-brain connection plays an important role here. Your gut microbiome produces neuromodulatory molecules that influence brain function, and dysbiosis—imbalanced gut bacteria—is linked to both increased inflammation and cognitive symptoms.

Nutritional deficiencies directly impair brain function

Several nutrients are essential for cognitive health, and deficiencies can cause or worsen brain fog.

Vitamin B12 is crucial for nerve function and red blood cell production. Deficiency causes symptoms ranging from fatigue and "pins and needles" to confusion, memory problems, and depression. About five percent of adults aged 65-74 and more than 10 percent of those over 75 are deficient. Vegans, vegetarians, older adults, and people taking certain medications face elevated risk.

Iron carries oxygen to your brain. Even without full-blown anemia, low iron stores can cause fatigue and cognitive symptoms. Iron deficiency is particularly common in women of reproductive age.

Vitamin D receptors are widespread in brain regions important for cognition. Low levels are associated with cognitive impairment in observational studies, though intervention trials have been less conclusive.

Omega-3 fatty acids, particularly DHA, are structural components of brain cell membranes and reduce neuroinflammation. Deficiency is linked to memory problems and attention deficits.

Medical conditions commonly cause cognitive symptoms

Many health conditions include brain fog as a prominent symptom.

Thyroid disorders affect an estimated 46 percent of patients with brain fog before they're even diagnosed with thyroid problems. Both underactive and overactive thyroid can impair cognition, though the mechanisms differ.

Postural orthostatic tachycardia syndrome, or POTS, causes brain fog in over 95 percent of patients, usually through reduced cerebral blood flow when standing. Most POTS patients experience foggy thinking daily.

Fibromyalgia causes cognitive impairment in over half of patients—severe enough that some studies find cognitive performance similar to adults 20 years older. This phenomenon is often called "fibro fog."

Depression and anxiety both involve cognitive symptoms, though the relationship is bidirectional—inflammation and brain changes can cause both mood and cognitive symptoms.

Long COVID represents a major modern cause

The COVID-19 pandemic brought brain fog into mainstream awareness, with 22 to 32 percent of COVID survivors experiencing persistent cognitive symptoms at least 12 weeks after infection. Research has identified multiple mechanisms: neuroinflammation, blood-brain barrier disruption, microclot formation affecting brain blood flow, possible viral persistence, and immune system dysregulation.

Importantly, Long COVID brain fog occurs regardless of initial illness severity—people with mild infections are nearly as likely to develop cognitive symptoms as those who were hospitalized. A 2024 study in the New England Journal of Medicine involving nearly 113,000 participants confirmed that measurable cognitive deficits persist even in people who feel otherwise recovered.

Medications can impair cognition

Certain drug classes commonly cause cognitive side effects. Anticholinergic medications pose the highest risk—these include common antihistamines like diphenhydramine, some bladder medications, and older antidepressants. A six-year study found that regular anticholinergic use leads to long-term mild cognitive impairment, with increased brain atrophy visible on imaging.

Benzodiazepines—anti-anxiety medications like Valium and Xanax—impair memory consolidation. Some statins, proton pump inhibitors, and certain blood pressure medications have also been associated with cognitive symptoms in some people.

Blood sugar dysregulation affects brain energy

Your brain is an energy hog, consuming about 20 percent of your body's glucose. When blood sugar regulation is impaired—whether from diabetes, insulin resistance, or reactive hypoglycemia—cognitive function suffers. Research now describes Alzheimer's disease as potentially involving "Type 3 diabetes" because of the strong connections between brain insulin resistance and cognitive decline.

Dehydration impairs cognitive performance

A 2018 meta-analysis found that dehydration significantly impairs cognitive performance, particularly attention, executive function, and motor coordination. The effects become significant when fluid loss exceeds two percent of body weight, but even mild dehydration affects some people. Older adults and children are particularly vulnerable to cognitive effects from insufficient hydration.

Evidence-based strategies for clearing brain fog

Now for the actionable part: what actually works. These interventions are organized by strength of evidence, from strongest to emerging.

Optimizing sleep has the strongest evidence

Given sleep's fundamental role in brain health, sleep optimization should be your first target if brain fog is affecting your life.

Cognitive Behavioral Therapy for Insomnia, or CBT-I, is the gold-standard treatment for sleep problems, outperforming sleep medications in long-term studies. A meta-analysis of 20 randomized controlled trials found that CBT-I reduces the time to fall asleep by an average of 19 minutes, decreases nighttime wakefulness by 26 minutes, and improves sleep efficiency by 10 percent. About 70 to 80 percent of people with chronic insomnia experience improvement.

CBT-I includes several components: sleep restriction (limiting time in bed to match actual sleep time), stimulus control (using the bed only for sleep), cognitive restructuring (addressing unhelpful thoughts about sleep), and relaxation training. Digital versions—apps like CBT-I Coach or programs like Sleepio—show effectiveness comparable to in-person therapy when access is limited.

Practical sleep hygiene steps with research support include maintaining a consistent sleep schedule (including weekends) for circadian rhythm alignment, keeping your bedroom cool, dark, and quiet, avoiding screens for at least 30 minutes before bed (blue light suppresses melatonin), limiting caffeine after early afternoon, getting morning light exposure to regulate your circadian clock, and targeting seven to nine hours of sleep per night.

Exercise improves cognition through multiple mechanisms

Exercise is one of the most powerful interventions for brain health, with effects comparable to or exceeding cognitive training programs.

The BDNF connection matters here. Exercise stimulates production of brain-derived neurotrophic factor, or BDNF, a protein that supports neuron growth, survival, and plasticity. A meta-analysis of 29 studies found that a single exercise session produces a moderate increase in BDNF, and regular exercise amplifies this effect. Higher BDNF levels correlate with better memory across multiple studies.

A 2025 meta-analysis of 35 randomized controlled trials found that combined aerobic and resistance training produces the strongest cognitive effects. The optimal parameters from research: three to four sessions per week, 30 to 60 minutes per session (interestingly, sessions under 45 minutes showed the largest effects), moderate intensity (50 to 75 percent of maximum heart rate), aerobic exercise combined with resistance training, and program lengths of 12 to 26 weeks showing robust effects, though benefits appear within four weeks.

Yoga and mind-body exercise also show cognitive benefits. A meta-analysis found moderate effect sizes for acute yoga sessions, with memory showing the strongest improvement. Regular yoga practice is associated with increased hippocampal gray matter volume.

Stress management directly addresses inflammation

Given stress's role in neuroinflammation and cortisol-mediated brain changes, stress reduction isn't just about feeling calmer—it's about protecting your brain.

Mindfulness meditation has strong evidence. A comprehensive 2023 meta-analysis of 111 randomized controlled trials with over 9,500 participants found that mindfulness-based interventions consistently improve cognitive function. The effects were significant for working memory accuracy, sustained attention, inhibition (ability to suppress irrelevant information), cognitive flexibility, and global cognitive function.

Importantly, the benefits were stronger for people with elevated stress or psychiatric symptoms compared to healthy controls—meaning those who need it most benefit most. You don't need lengthy meditation sessions. The meta-analysis found no dose-response relationship, meaning even brief practices can be effective. What matters more is consistency.

Specific breathing techniques show promise. A Stanford study comparing breathing exercises to meditation found that cyclic sighing—a technique involving extended exhalations—produced greater mood improvements than mindfulness meditation over one month. Research supports slow breathing rates (4.5 to six breaths per minute), sessions of at least five minutes, and emphasis on extended exhale (exhaling longer than inhaling).

This slow, diaphragmatic breathing increases vagal tone and shifts your nervous system toward rest-and-digest mode, reducing stress hormones and inflammation.

Nutritional interventions support brain function

The Mediterranean diet has the strongest evidence for cognitive protection. Meta-analyses show 23 to 35 percent reduced dementia risk with high adherence, and the diet preserves brain volume over time. The key components: olive oil, fish two to three times weekly, abundant vegetables (especially leafy greens), berries, nuts, and limited red meat and processed foods.

Omega-3 supplementation shows moderate evidence. A 2025 systematic review of 58 randomized controlled trials found that omega-3 fatty acids, particularly DHA and EPA, produce modest improvements across cognitive domains, with optimal doses around 1,000 to 2,500 milligrams daily. The effects are stronger in people with mild cognitive impairment than in those with established dementia or already-healthy young adults.

Here's a critical distinction about supplements: they dramatically improve brain fog if you're deficient, but don't expect miracles if your levels are normal. B12 supplementation dramatically improves brain fog if you're deficient, but a meta-analysis of 16 trials found no benefit for people with normal levels. Vitamin D supplementation didn't improve cognition in a 2025 trial of 620 adults with mild-to-moderate deficiency, despite strong observational associations. Magnesium shows a U-shaped relationship with cognition—both low and high levels are problematic, suggesting maintaining optimal levels matters more than supplementing.

Caffeine combined with L-theanine shows consistent benefits for acute focus and attention. Multiple studies confirm the combination is superior to either substance alone, with L-theanine (found naturally in tea) smoothing out caffeine's jittery effects. Typical effective doses: 40 to 100 milligrams caffeine with 100 to 200 milligrams L-theanine.

Stay adequately hydrated. While you don't need to obsess about drinking eight glasses daily (individual needs vary), ensuring adequate hydration is a simple fix that can meaningfully impact cognition, especially if you tend toward dehydration.

What about popular supplements?

Lion's mane mushroom generates significant interest, but human evidence remains preliminary. Small, short-duration studies show mixed results, and preclinical findings on nerve growth factor stimulation haven't been replicated in humans. It's generally safe but insufficient evidence exists to recommend it for brain fog.

Ginkgo biloba doesn't improve cognition in healthy adults according to meta-analyses, despite extensive marketing claims.

Phosphatidylserine has moderate evidence for memory support, particularly in older adults.

Many commercial "brain fog" supplement stacks contain multiple ingredients at doses too small to be effective. Be skeptical of products with ten or more ingredients in a proprietary blend.

When to see a doctor

Brain fog warrants medical evaluation when it's sudden onset or rapidly progressive, accompanied by neurological symptoms like vision changes, weakness, numbness, or speech difficulties, occurs after recently starting new medications, comes with significant unexplained weight changes, happens alongside a chronic health condition like diabetes or autoimmune disease, persists despite lifestyle improvements, or significantly impairs your daily functioning or work performance.

Request comprehensive bloodwork including thyroid panel (TSH, free T4, free T3, and thyroid antibodies), complete blood count, vitamin B12, vitamin D, iron and ferritin, and basic metabolic panel. These relatively simple tests can identify treatable causes in many people.

For brain fog following COVID-19 infection, specialized Long COVID clinics are becoming more available. Emerging treatments include hyperbaric oxygen therapy, which showed significant cognitive improvements in the first randomized controlled trial (improvements in global cognitive function, attention, and executive function), and various forms of brain stimulation therapy.

Practical implementation: Your action plan

The first two weeks focus on assessment and baseline improvements. Track your brain fog patterns: When is it worst? After poor sleep? Certain foods? Times of day? Start a consistent sleep schedule, begin daily hydration tracking, and schedule bloodwork with your doctor.

Weeks three and four add movement. Start with 20 to 30 minute walks, three to four times weekly. Gradually increase to include some higher-intensity exercise. Add simple resistance exercises like bodyweight squats and pushups.

Weeks five and six address stress. Practice five-minute breathing exercises daily using the extended exhale technique. Try a guided meditation app—even 10 minutes daily helps. Identify your top stressors and one concrete step to address each.

Weeks seven and eight optimize nutrition. Shift toward Mediterranean diet patterns. Consider omega-3 supplementation (1,000 to 2,000 milligrams daily) if dietary intake is low. Correct any identified deficiencies based on bloodwork.

Most people notice improvements within four to six weeks of consistent lifestyle changes, with continued gains over three to six months. Some causes—like severe B12 deficiency or untreated thyroid disease—improve faster once properly treated. Long COVID brain fog has more variable timelines, with some people improving within months and others requiring a year or longer.

The bottom line

Brain fog is real, it has identifiable causes, and it responds to intervention. The strongest evidence supports a multi-pronged approach: optimize sleep, exercise regularly, manage stress, eat a Mediterranean-style diet, and correct any underlying deficiencies or conditions. These aren't quick fixes, but they address root causes rather than just masking symptoms.

Start with sleep—it's foundational to every other cognitive function. Add movement, which produces benefits within weeks. Address stress, which may be driving inflammation you can't see. And if improvements plateau, work with a healthcare provider to investigate underlying causes.

Your brain is remarkably adaptable. Give it what it needs, and the fog can lift.