15 Possible Causes of Brain Fogginess

Foggy, dry, or cloudy thinking could be stress or one of these other conditions.

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We all likely have experienced "brain fog"—a term used to describe the sluggish, cloudy feeling you get in your head when you can't focus, feel exhausted but can't sleep, forget things, or start making simple mistakes. But brain fog exists on a spectrum. For some, it is a frustrating—even debilitating—everyday part of life.

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

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 difficulty 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 immediately. 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.


Lupus is a chronic autoimmune disease where your immune system mistakes your body's healthy cells as invaders 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 Resource Center on Lupus 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.

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").

MS brain fog "commonly affects the speed at which people can process information and also their ability to recall things," said Kathleen Costello, certified registered nurse practitioner and research associate at the Johns Hopkins MS Center in Baltimore. "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 having trouble making decisions.

A review published in March 2015 in the Multiple Sclerosis Journal 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 said.

"Every situation has to be looked at really individually," Costello added. Check with your healthcare provider to see if a medication can help and to ensure 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 challenging mental tasks sooner after you wake up.

Chronic Fatigue Syndrome (CFS)

It's no surprise that a condition where fatigue is the main symptom also brings brain fog. An overview published in 2013 in Frontiers in Physiology defines chronic fatigue syndrome (CFS) as 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 are often met with stigma and disbelief. Your brain fog may keep you from working or enjoying time with friends. This, and the frustrating symptoms, may also cause anxiety and depression.

Celiac Disease

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, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). 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. A study published in July 2014 in Alimentary Pharmacology and Therapeutics found that people with celiac disease who followed a strict gluten-free diet saw cognitive performance improve.


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." As you may guess, the brain might not exactly feel clear after a migraine.

A study published in July 2016 in Neurology evaluated the postdrome's symptoms and found that patients reported "feeling tired/weary, having difficulty concentrating and stiff neck."

Underactive Thyroid

Your 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, according to the NIDDK.

Thyroid-related brain fog means trouble concentrating, memory issues, spacing out, and confusion. However, the NIDDK 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 survey published in March 2022 in Endocrine Practice, patients with hypothyroidism who had reported feeling brain fog associated it most with fatigue and forgetfulness. Brain fog can be disruptive to everyday life. In a review published in May 2022 in Thyroid, researchers noted brain fog left people with hypothyroidism feeling "distress and a diminished quality of life."


When a person's menstrual cycle ends permanently, they enter menopause. This typically occurs in your 40s or 50s. Brain fog is a lesser-known menopause symptom.

A review published in July 2016 in Menopause noted women going through menopause reported feeling forgetful and having difficulty concentrating. Previously, a 2013 study also published in Menopause found 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.


You have likely heard the term "pregnancy brain" when referring to the brain fog pregnant people experience.

Understanding how pregnancy affects cognitive ability requires more research. However, in a study published in May 2014 in the Journal of Clinical and Experimental Neuropsychology, pregnant and postpartum people 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 healthcare provider about ways to make sleeping soundly while pregnant more possible.

Premenstrual Syndrome (PMS)

Premenstrual syndrome, better known as PMS, brings with it a slew of symptoms: abdominal and back pain, headache, nausea, and anxiety, to name just a few. Premenstrual dysphoric disorder (PMDD) is a severe form of PMS. Both PMS and PMDD symptoms can range from uncomfortable to downright debilitating. Brain fog can also be a frustrating symptom. Some people call this "period brain."

Hormones like estrogen and progesterone, which fluctuate throughout a person's menstrual cycle, seem to influence cognitive function, according to a review published in April 2020 in Brain Sciences. The review also noted that people have described having difficulty concentrating in their late luteal phase (after ovulation and before their period begins).

Depression and Anxiety

You may associate depression with feeling sad or losing interest in your favorite activities, but it also can affect how you feel and think, according to the National Institute of Mental Health (NIMH). You may actually find your thinking and speaking slows down, or you have difficulty focusing, making decisions, and remembering things, as found in a review published in September 2015 in Annals of General Psychology.

Anxiety disorders can also cause brain fog, according to a review published in March 2016 in Psychological Bulletin. Unfortunately, the aftermath of depression and anxiety brain fog could lead to worse feelings about yourself and make it difficult to reach out for help. But you do have options.

Many effective medications and forms of therapy to treat depression and anxiety might help with cognitive symptoms, too.

Sleep Disorders

Most of us know how 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 healthcare provider to understand if you have an isolated sleeping disorder or if an underlying cause 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, particularly 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 severe brain fog. Feeling tired throughout the day may leave you unable to pay attention or make decisions, according to a study published in May 2019 in Accident Analysis & Prevention. You may often feel confused or have difficulty completing tasks. A study published in December 2016 in the Journal of Sleep Research also found that sleep deprivation can lead to the creation of false memories.

Sjogren's Syndrome

The classic symptoms of the chronic inflammatory autoimmune disease Sjogren's syndrome are dry eyes and dry mouth, according to the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). Brain fog can also be part of the equation. Again, the fog usually involves memory lapses and poor concentration.

A systematic review published in April 2019 in Brain Sciences 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 relationship between Sjogren's and cognitive dysfunction, noting the brain fog may be a result of another Sjogren's symptom: fatigue.


Fibromyalgia affects about 2% of the adult U.S. population and is seen more often in women than men, according to the CDC. 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 correctly diagnosed.

People with fibromyalgia report experiencing brain fog, sometimes called "fibro fog," which includes forgetfulness, difficulty concentrating, and, you guessed it, brain fogginess, according to a study published in July 2015 in Rheumatology International. Furthermore, a study published in March 2018 in Frontiers in Psychology observed how fibromyalgia could bring cognitive impairments. Fibromyalgia pain also makes it difficult to sleep and comes with increased fatigue, two things that can exasperate brain fog.


Cirrhosis of the liver is a type of chronic liver disease most commonly caused by heavy alcohol use or hepatitis C, according to the CDC. 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," said 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, Dr. Taddei added. It can cause minor symptoms like irritability, but in severe cases, it can also lead to a coma.

If you have cirrhosis, talk to a healthcare provider to find a treatment plan. The NIDDK also recommends you stop drinking alcohol.

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