15 Conditions That Can Cause Serious Brain Fog

Does your brain feel foggy, dry, or cloudy? You might just be stressed–or one of these conditions could be to blame.

"Brain fog" is not a technical medical condition, but it is a symptom. We all likely have experienced levels of brain fog -- that sluggish, cloudy feeling you get in your head when you can't focus, feel exhausted but maybe can't sleep, forget things, or start making simple mistakes. But brain fog exists on a spectrum, and for some, it is a frustrating, sometimes debilitating everyday part of life.

Brain fog can come with stress, poor sleep, and overexertion that likely creep up occasionally, but if yours is persistent, gets in the way of your day-to-day life, or is negatively affecting your mental health, you should talk with a physician. There may be an underlying cause.

Read on to find conditions that often come with brain fog.

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Lyme disease

Lyme disease, transmitted through the bite of an infected tick, often starts with the classic "bulls-eye" rash and then can progress into multiple symptoms, including brain fog.

The mental fuzziness can come on anytime after being infected and usually involves having a hard time keeping up with conversations, retaining information, or finding the right word.

If you have brain fog and you know you've been bitten by a tick, seek medical help right away. If you didn't see a tick but you do see the bulls-eye rash, same deal. Most people who are treated early (usually with antibiotics) recover.

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Lupus is a chronic autoimmune disease where your immune system mistakes your body's healthy cells as invadors and attacks them, causing inflammation and pain. Systemic lupus erythematosus (SLE), the most common form of the disease, affects 200,000 adults in the U.S., according to the CDC. Its cause is unknown.

The lupus community sometimes refers to brain fog as "lupus fog." It presents itself as lapses in memory, difficulty concentrating, and confusion. The National Resoure Center on Lupus also notes you may have trouble completing familiar tasks, remembering names, keeping a schedule, and processing thoughts.

In some people, the symptoms are bad enough to interfere significantly with daily life. Lupus-related brain fog usually ebbs and flows. Talk to your healthcare provider about lupus treatments that can address your symptoms and ways to circumvent your memory issues.

The National Resource Center on Lupus also suggests reading books, doing puzzles, and using planners or color-coded calendars.

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Multiple sclerosis

Multiple sclerosis is a chronic inflammatory disease where lesions on the central nervous system can affect motor function, emotions, cognition, or how clearly you think. People with MS sometimes refer to their brain fog experience as "cog fog" (short for "cognitive fog").

Cog fog "commonly affects the speed at which people can process information and also their ability to recall things," says certified registered nurse practitioner Kathleen Costello, associate vice president of healthcare access at the National Multiple Sclerosis Society in New York City. "If you tell me to call you tomorrow at 5, that is in and out of my head."

The National Multiple Sclerosis Society notes that brain fog may leave you struggling to find the right words, having difficulty remembering how to do a job or task, and finding trouble making decisions.

A 2014 study also observed an overlap of multiple sclerosis with sleep disorders. Having no or restless sleep can exasperate brain fog.

Brain fog may get worse during multiple sclerosis flares and can be exacerbated by heat on a hot day, in a hot room, or when you have a fever, Costello says.

"Every situation has to be looked at really individually," she adds. Check with your doctor to see if medication can help and to make sure nothing else (like depression or meds for other symptoms) is causing your brain fog. Then talk about work-around strategies. For instance, if your brain gets hazy at the end of the day, consider doing tough mental tasks sooner after you wake up.

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Chronic fatigue syndrome (CFS)

It's no surprise that a condition where fatigue is the main symptom also brings mental fuzziness. The NIH defines chronic fatigue syndrome (CFS) as a physical and cognitive fatigue that lasts more than six months. Also known as myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), it's not improved with rest or sparked after a high-energy day. People with CFS describe experiencing sluggish or hazy thinking, difficulty focusing and concentrating and forgetfulness.

The condition's cause is still unknown; a 2014 study in the Journal of Nuclear Medicine examined "widespread" neuroinflammation in people with CFS and determined this may be essential in developing diagnostic criteria and treatment.

People who have CFS often are met with stigma and disbelief. Your brain fog may keep you from working or enjoying time with friends. This, along with the frustrating symptoms themselves, may also cause anxiety and depression.

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Celiac disease

Scientists are only beginning to understand the myriad ways our gut influences different parts of our body. Celiac disease is a good example of a condition that starts with the gut but can result in symptoms all over.

When people with celiac disease eat gluten, a protein found in wheat and other grains, the immune system attacks the small intestine, producing an array of gut-related symptoms like abdominal pain or bloating, diarrhea, and constipation. But other symptoms, like fatigue, joint pain, or mouth sores can also crop up–and some may even affect your brain.

People with celiac-related brain fog report feeling disoriented, unable to focus or pay attention, and forgetful. In one study, people with celiac disease had the same level of cognitive impairment as someone with a blood alcohol level of 0.05. (The legal limit for driving is 0.08.)

People with celiac disease need to avoid gluten. Not only will it calm your stomach, it can clear your brain.

06 of 15


Migraines are severely debilitating, with symptoms ranging from intense head pain to nausea, vomiting, and fatigue. This can create a foggy feeling in your brain, to say the least.

The American Migraine Foundation reports you may experience brain fog up to 48 hours before and 24 hours after a migraine. In the hours or days after a migraine, this brain fog may be part of what some migraine patients call a "migraine hangover," also known as "postdrome." This is the final of four migraine phases. As you may guess, the brain might not exactly feel clear after a migraine.

A 2016 study evaluating the postdrome's symtoms found that patients reported "feeling tired/weary, having difficulty concentrating and stiff neck."

07 of 15

Underactive thyroid

Thyroid hormone controls your body's energy. When it's gone awry, you can feel it all over. An underactive thyroid (hypothyroidism) can lead to weight gain, sluggishness, and depression, and thinking can feel like slogging through molasses. Thyroid-related brain fog means trouble concentrating, memory issues, spacing out, and confusion. However, the NIH notes that hypothyroidism can progress slowly, so you may not notice it at first and perhaps mistake brain fog for just a cloudy day in your head.

In a 2022 survey of patients with hypothyroidism who had reported feeling brain fog found that patients associated their brain fog most with fatigue and forgetfulness. This left patients feeling "distress and a diminished quality of life."

Some people may need treatment in the form of synthetic thyroid hormone.

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When a woman's menstrual cycle ends permenantly she enters menopause. This typically occurs in your 40s or 50s. (Stereotypical) media depict women going through menopause sticking their heads in freezers to stave off night sweats, or losing their hair. Those are real symptoms (and no judgment if the freezer has helped you cool down), but brain fog is a lesser-known menopause symptom.

A 2016 study found women going through menopause reported feeling forgetful and having difficulty concentrating. A 2013 study previously noted that women first transitioning into menopause experienced more cognition issues--specifically, verbal learning and memory, motor function, and paying attention--than women in later menopausal stages. So it seems as you first enter menopause, you may feel more brain fog.

09 of 15


You have likely heard the terms "pregnancy brain" or "baby brain" when referring to the brain fog pregnant women experience. Researchers are still studying if and how pregnancy affects cognitive ability.

However, in a 2014 study, pregnant and postpartum women did more commonly self-report memory difficulties.

Of course, pregnancy can also affect your quality of sleep. General discomfort, having to pee, back pain, heartburn, leg cramps, and anxiety may all be a part of your pregnancy, and certainly make it difficult to get sound shut-eye, which can, in turn, cause tiredness and brain fog. Talk to your doctor about ways to make sleeping soundly while pregnant more possible.

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Premenstrual symdrome, better known as PMS, brings with it a sleu of symptoms: abdominial and back pain, headache, nausea, anxiety, to name just a few. They can range from uncomfortable to downright debilitating. You can add brain fog to that list. Some women call this "period brain."

Premenstrual dysphoric disorder (PMDD) is more severe form of PMS. We still need more research to understand PMS and PMDD's effect on cognitive ability. We do know that hormones like estrogen and proestrogen, which flucuate throughout a person's menstrual cycle, seem to influence cognitive function. Women have also described having difficulty concentrating in their late luteal phase (after ovulation and before their period begins).

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Depression and anxiety

You could argue that depression is the very embodiment of brain fog, clincally called "cognitive dysfunction." Not only do you feel sad and lose interest in your favorite activities, you may find your thinking and speaking slows down or you have difficulty focusing, making decisions, and remembering things. Getting everyday tasks done may feel impossible, it may be difficult to pay attention, and you may be slow to react. Anxiety, which commonly occurs with depression, can also cause brain fog. Unfortunately, the aftermath of depression brainfog could lead to worse feelings about yourself and make it difficult to reach out for help. But you do have options.

There are many effective medications and forms of therapy to treat depression that might help with cognitive symptoms, too.

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Sleep disorders

Most of us are familiar with the way our mental processes slow after a restless night. It happens!

But people with diagnosed sleep disorders may have more severe and more frequent brain fog. You should talk to your doctor to understand if you have an isolated sleeping disorder or if an underlying cause exists that makes it difficult to fall or stay asleep.

The most common sleep disorders, according to the CDC, include insomnia, the inability to sleep; narcolepsy, excessive daytime sleepiness; restless legs syndrome, a "creeping" sensation that causes leg pain particuarly at night; and sleep apnea, when you appear to "gasp," snore, or stop and begin breathing while you sleep.

As you may expect, sleep deprivation can lead to serious forms of brain fog. Feeling tired throughout the day may leave you unable to pay attention or make decisions. You may feel confused often or have difficulty completing tasks. A 2016 study also found that sleep deprivation can lead to the creation of false memories.

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Sjogren's syndrome

The classic symptoms of the chronic inflammatory autoimmune disease Sjogren's syndrome are dry eyes and dry mouth, but brain fog can also be part of the equation. Again, the fog usually involves memory lapses and poor concentration.

A 2019 systematic review found that in some cases, cognitive challenges were the "first clinical manifestation" of Sjogren's, appearing before an official diagnosis was made. Researchers concluded that further studies are required to understand the true relationship between Sjogren's and cognitive dysfunction, noting the brain fog may be a result of another Sjogren's symptom: fatigue.

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Fibromyalgia, a condition that affects about 2% of the adult U.S. population, is seen more often in women than men. It is a chronic disorder that causes widespread tenderness and musculoskeletal pain, along with fatigue, memory problems, and more. There is no specific test for the condition, so it can take time to be properly diagnosed.

People with fibromyalgia report experiencing brain fog, sometimes called "fibro fog," which includes forgetfulness, difficulty concentrating, and, you guessed it, brain fogginess. And numerous studies have observed how fibro can bring with it cognitive impairments. Fibromyalgia pain also makes it difficult to sleep and comes with increased fatigue, two things that can exasperate brain fog.

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Cirrhosis of the liver is a type of chronic liver disease most commonly caused by heavy alcohol use or hepatitis C. People with cirrhosis can develop a condition called hepatic encephalopathy (HE), a nervous system disorder, which can have cognitive effects.

"HE happens when the body builds up ammonia because the liver is not doing a good job metabolizing it," says Tamar H. Taddei, MD, a member of the American Liver Foundation's National Medical Advisory Committee and an associate professor at Yale School of Medicine. "It can go to the brain and cause what you could call brain fog." HE is a very serious condition, she adds. It can cause relatively minor symptoms like irritability, but in severe cases it can also lead to a coma.

Fortunately, a drug called lactulose can reduce ammonia and treat HE and liver disease. Sometimes antibiotics are also used for HE.

Because hepatitis C is not only treatable but curable, hepatic encephalopathy is avoidable. Cirrhosis is preventable and treatable as well, not only by taking care of hep C, but also by cutting down on alcohol, eating nutritiously, and being careful with medications (since some can damage the liver).

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