Maybe you keep walking into a room and forgetting why. Or maybe you have to reread the same email 3 times until you can actually process it. Meet: Brain fog, a term coined for a range of symptoms including your ability to think clearly, focus, concentrate, remember, and pay attention. When people experience these symptoms, they often chalk it up to stress and move on.
While stress can definitely be one cause of brain fog, there are other factors that can contribute to or cause brain fog. In this article we’ll dig into what brain fog feels like, the most common causes, and the labs that can help you pinpoint what might be causing yours.
What Does Brain Fog Feel Like?
Brain fog might feel different to each individual. Some people describe brain fog as “having to work really hard just to think:”, like their “brain is in slow motion,” or like they’re “walking through sludge.”
However you describe it, just know that your symptoms are real and you’re not alone. And because brain fog symptoms vary from person to person, finding the root cause of your brain fog is key.
Can Stress & Anxiety Cause Brain Fog?
Yes. Stress and anxiety are two common causes of brain fog. Short term stress can give you a burst of cortisol, which helps you focus. Think about the five minutes before a big presentation. Your heart beats faster, your thoughts get sharp, and you remember every point on your slides. That’s cortisol doing its job. The trouble starts when your body acts like you’re about to present all day, every day, for months. Cortisol pumping through your body daily actually makes memory and focus harder.
Anxiety eats up mental bandwidth. When part of your brain is scanning for threats, there’s less room left to remember the details of life: grocery lists, why you walked into a room, or what that email your boss sent is asking.
Then there’s the inevitable loop: brain fog makes you anxious about slipping up at work, which adds stress, which deepens the fog.
Other Brain Fog Causes Worth Ruling Out
While stress and anxiety are common causes of brain fog, there can be other root causes too.
Thyroid Changes
Your thyroid is a small gland in your neck that sets the pace for almost everything your body does, including how fast your brain works. When it runs slow, thinking can feel dull and heavy. One woman in a study on hypothyroidism and brain fog put it simply: “Feels like I am walking through sludge.” You might also notice you’re tired no matter how much you sleep, or you’re always reaching for a sweater.
On the other hand, an overactive thyroid can feel like anxiety and restless nights. Many people mistake it for true anxiety, and some spend years treating the wrong thing.
In conventional medicine, some of your thyroid levels are checked annually, like TSH. It’s a helpful starting point, but doesn’t tell the whole story. A full thyroid panel goes beyond TSH and looks at free T3, free T4, reverse T3, and thyroid antibodies, so your provider can see how your thyroid is actually working
Hormone Shifts in Perimenopause and Menopause
Your hormones do more for your brain than most people realize. Estrogen helps brain cells form new connections and keeps blood flowing to the areas that handle memory. Progesterone has a calming effect and supports deep sleep, which your brain needs to store what you learned that day. Women also make testosterone, and it helps with focus and mental sharpness.
During perimenopause, these levels start to drop and swing up and down. That can show up as brain fog, trouble finding words, or anxiety that seems to come out of nowhere. Plenty of women in their 40s blame stress first, and stress may be part of it. Advanced hormone testing can show whether your levels are part of the picture too.
If they are, the right type and dose of bioidentical hormone replacement therapy may help. Many women notice clearer thinking and better sleep once their hormones are back in balance.
Poor Sleep
A lack of quality sleep can be another cause of brain fog, which ties back to stress. When cortisol levels are running high, especially around bedtime, you can stay wired and have trouble getting enough sleep.
In a recent study, researchers watched the brain activity of volunteers after a night without enough sleep. They tested them by having them quickly sort images and their brains responded slower than usual.
When you’re short on sleep, your brain cells have a harder time talking to each other. That lag matters. It means your brain takes longer to turn what you see into a clear though. If you’ve ever stared at an email on your screen and couldn’t make it register after a bad night of sleep, that’s what’s happening.
Low Nutrients
Your brain needs a steady supply of certain nutrients to work well, and running low on a few of them can leave you feeling foggy. Vitamin B12 is a big one. When levels drop, you might feel tired or weak, and some people notice memory slips or confusion too, according to the National Institutes of Health. B12 levels often fall slowly over the years, so the fog can creep in without you noticing. Your body also absorbs less B12 as you age, and some common medications, like metformin and acid reflux pills, can make it harder to absorb.
Iron matters too, especially for women who still get their periods. Low iron can make it harder to focus and leave you worn out. Many women are told their blood work looks fine because they aren’t anemic, but low iron without anemia is at least twice as common and can still cause fatigue and trouble thinking clearly. A standard blood count won’t always catch it. Checking ferritin, which measures how much iron your body has stored, gives a clearer answer.
Vitamin D may play a part as well. Low levels are common, especially in winter, and easy to check with a simple blood test.
If your fog won’t lift, advanced lab testing can show whether any of these levels are off.
Mold Exposure
Mold is everywhere, but certain types of mold produce toxins known as mycotoxins. When a person is routinely exposed to mold, like when they live in or work in a water-damaged building, they can experience a wide range of health problems, including brain fog. People suffering from mold toxicity might feel a loss of focus, difficulty with word finding, problem solving, memory loss, and confusion along with mood changes like anxiety and depression.
Fortunately, Forum Health can help determine the extent of your toxin buildup through comprehensive mycotoxin testing and can support you through the detox process through diet changes and more.
Lyme Disease
Lyme can be hard to spot. The ticks that carry it can be as small as a poppy seed, so many people never notice a bite. Not everyone gets the bullseye rash either. When symptoms show up weeks or months later as achy joints or a foggy head, it’s easy to blame stress, a busy schedule, or getting older.
Brain fog with Lyme isn’t in your head, at least not the way people sometimes suggest. The bacteria that cause Lyme can reach the nervous system, which can bring on memory problems and trouble concentrating. For some people, those symptoms stick around even after antibiotics. In a 2022 study, Johns Hopkins researchers used advanced brain scans on people with lingering Lyme symptoms. They found changes in brain structure and activity that they didn’t see in people without Lyme. That’s a big deal for patients who’ve been told their tests look normal.
If you live in or have visited an area with ticks and your fog came with joint pain or fatigue you can’t explain, it’s worth asking about Lyme testing.
Is There a Brain Fog Test?
Currently, there’s no easy, standard brain fog test. Brain fog is a symptom, so the real question is what’s behind it. A routine checkup usually covers a basic blood count and maybe a TSH. If those look normal, many people leave without answers, still foggy and now wondering if it’s all in their head.
What You Can Try This Week
You don’t need a lab report to start feeling a little clearer. Small changes can take the edge off stress-related fog.
Start with a consistent wake-up time––yes, even on weekends. Sleeping in on weekends can leave you groggy well into Monday.
Breakfast also matters. Many people skip breakfast or grab something sugary or processed. Try eggs, Greek yogurt, or a protein smoothie instead. That 3 pm sugary snack matters too, as sugar can make you feel more tired and less alert.
After lunch, try a ten minute walk. It doesn’t have to be a cardio workout. The point is to get more sunlight during the day to help reset your body clock.
During particularly stressful times, give your brain a break between tasks. Step away from your computer for a few minutes, take a few deep breaths, or stand and stretch. Jumping from meeting to meeting all day keeps your stress response switched on all day.
Last, keep a brain fog log for a couple of weeks. Note when you feel cloudy, what you ate, how you slept, and anything stressful that happened. It’s quick but can make a huge impact if you notice any patterns.
These steps can help when stress or poor sleep are the reasons behind your fog. They won’t fix a thyroid problem, low iron, or Lyme. If you’ve given it a few weeks and you’re still feeling foggy, your log is a great thing to bring to your first appointment.
How Forum Health Gets to the Root of Brain Fog
Many people come to Forum looking for a natural treatment for brain fog after hearing “your labs are normal” more than once. Our providers spend an average of one hour with each patient per visit, so there’s time to talk through when the fog started and what makes it worse. Maybe it hits after lunch, or it’s been heavier since your sleep fell apart last spring. Those details shape which tests your provider orders through Forum Labs, from thyroid and hormones to iron and vitamin levels. If your history points that way, Lyme or mycotoxin testing may be added too.
Your results come back in Forum Insights, a report that explains what your numbers mean in plain language. Fog often has more than one cause, and seeing everything side by side helps your provider connect the dots. From there, you build a plan together. It might include nutrition changes, supplements to fill gaps, better sleep habits, or hormone therapy if your levels call for it. Your provider will retest and check in on how you actually feel, and the plan changes if the fog hasn’t lifted.
Forum Foundation is the place to start. It pairs advanced diagnostic testing with provider and health coach visits, so you’re not left to make sense of your results alone.
FAQs
Can stress and anxiety cause brain fog?
Yes. Ongoing stress keeps cortisol high, and over time that can make it harder to focus and remember things. Anxiety also takes up mental space, since part of your brain stays busy scanning for problems. If your fog lifts on vacation or after a hard season ends, that’s a good clue stress is involved.
How long does brain fog from stress last?
It depends on what’s behind it. Fog from a rough week or a few bad nights often clears within days once you catch up on rest. Long-term stress can keep it going for months. If you haven’t noticed a change after a few weeks of better sleep and lower stress, something else may be adding to it.
Is brain fog a sign of something serious?
Most of the time, brain fog comes from something common and treatable, like poor sleep, stress, hormone shifts, or low nutrient levels. It’s rarely an early sign of dementia. Get emergency care right away, though, if confusion comes on suddenly or you have trouble speaking, a severe headache, or weakness on one side of your body.
Can Lyme disease cause brain fog years later?
It can. Some people treated for Lyme still deal with fatigue and memory problems months or even years afterward. Johns Hopkins researchers have found measurable brain changes in these patients, which means the symptoms are real. If you’ve had Lyme and your fog never fully went away, mention it to your provider.
What kind of doctor should I see for brain fog
A primary care doctor is a good place to start, especially to rule out anything urgent. If your basic labs come back normal and you still feel foggy, a functional medicine provider can dig deeper with advanced testing. Forum visits average about an hour, so there’s time to go through your full history.
Sources
- Cleveland Clinic. “Brain Fog.” Cleveland Clinic Health Library. Updated May 14, 2024. https://my.clevelandclinic.org/health/symptoms/brain-fog
- The Menopause Charity. “Brain Fog.” Updated October 2022. https://themenopausecharity.org/information-and-support/symptoms/brain-fog/
- Ettleson MD, et al. “Brain Fog in Hypothyroidism: Understanding the Patient’s Perspective.” Endocrine Practice. 2022;28(3):257–264. doi:10.1016/j.eprac.2021.12.003. https://pmc.ncbi.nlm.nih.gov/articles/PMC8901556/
- Schmidt E. “Spacing Out After Staying Up Late? Here’s Why.” UCLA Health. November 6, 2017. https://www.uclahealth.org/news/spacing-out-after-staying-up-late-heres-why
- “The Relationship Between Iron Status, Cognitive Performance, Subjective Mood and Fatigue in Women of Reproductive Age.” ClinicalTrials.gov, NCT04257669. https://clinicaltrials.gov/study/NCT04257669
- Johns Hopkins Lyme Disease Research Center. “Is Lyme Disease Associated Brain Fog Real?” May 13, 2024. https://www.hopkinslyme.org/lyme-education/is-lyme-disease-associated-brain-fog-real/
