What Causes Brain Fog?

What Is Brain Fog?

Brain fog treatment depends upon the symptoms and causes.
Brain fog treatment depends upon the symptoms and causes.

Ever felt fuzzy-headed or unable to focus? That’s brain fog. It isn’t a medical condition or a diagnosis. Brain fog is a term that describes problems with focus, memory, logic, and problem-solving. Alone, it isn’t usually a sign that you have another medical condition. But sometimes it can be one of several signs of a health problem that needs a doctor’s care. Here is information about its causes that will help you know which ones require medical attention.

Stress, Anxiety, Depression

Feeling blue or stressed out once in a while is normal. But if you’ve been anxious, on edge, sad, or hopeless for more than two weeks, you might find it hard to think clearly. That’s because depression, anxiety, and even high stress can be mentally exhausting. These feelings can steal your focus from your day-to-day tasks.

If depression or anxiety are behind your brain fog, you might have these other symptoms:

  • Sense of hopelessness, constant worrying, sadness, or “empty” feeling
  • Feelings of guilt, worthlessness, helplessness
  • Loss of interest in or inability to enjoy activities you usually like
  • Low energy
  • Loss of appetite and weight loss or overeating and weight gain
  • Changes in sleep patterns

If you think you have depression or ongoing anxiety, see a doctor. Going without help can make it worse. Medication, talk therapy, or often both can help.

Lack of Sleep

Less than 7 to 8 hours of sleep a night can sap your memory and concentration. Good sleep allows your brain to rest and recover so it can function at its best when you’re awake. Try to set a bedtime that allows you 7 hours of sleep and stick to it.

If you’re in bed for seven or so hours but don’t feel your sleep is restful, you might have a sleep disorder. In sleep apnea, for example, you temporarily stop breathing repeatedly throughout the night. This causes interrupted, poor quality sleep. It can also cause brain fog.

If you have sleep apnea, you might also:

  • Wake up feeling exhausted
  • Snore
  • Wake up gasping or choking
  • Have a headache or dry mouth in the morning

In addition, your partner may notice that you stop breathing in your sleep.

If you think you have sleep apnea, talk to your doctor. Treatment can help improve your sleep and your focus. Without treatment, the condition can increase your risk for other serious health problems.

Menopause or Other Hormone Changes

Hormone changes can do a number on your focus. Some causes of hormone changes are:

The fluctuating levels of estrogen and progestin can dull your focus. What’s more, night sweats during perimenopause and menopause can make it hard to sleep. That can leave you feeling groggy the next day.

If hormone changes are causing brain fog, most women notice that the fog clears shortly after their hormone levels stabilize. That could be a few months after having a baby, changing birth control, or going through menopause.


Medicines called anticholinergics can make you foggy, too. These medications block the effects of a neurotransmitter in the brain and make it difficult to think clearly. Here are a few anticholinergics:

Chemotherapy (or chemo) medications for cancer may also leave you feeling fuzzy. Some people call this “chemo-brain.” In many cases, chemo brain clears after you finish your cancer treatment.

Talk to your doctor or pharmacist if you suspect one of your medications is making you feel foggy. You might be able to lower your dose or switch to something else.

Low Levels of Vitamin B12

You need a range of nutrients to stay healthy. Vitamin B12 is especially important for maintaining healthy nerves and blood. When you don’t get enough of it, you may find it hard to focus. Some people don’t eat enough B12-rich foods like meat, eggs, and dairy products. Others may not absorb it properly. This can simply happen to some people. Or, it can be the result of weight-loss surgery.

Besides the loss of focus, other signs of low B12 include:

  • Muscle weakness
  • Numbness or tingling in hands, legs, or feet
  • Difficulty walking
  • Feeling very tired or weak

Your body has a harder time absorbing B12 as you get older. If you think you’re low on B12, talk to your doctor. Your body needs this vitamin in order to function. Depending on your level, you may need B12 shots or pills or a daily multivitamin.

Multiple Sclerosis

Multiple sclerosis affects the central nervous system. With MS, your body doesn’t send information between your brain and other parts of your body the way it should. That can make it hard to concentrate, problem-solve, focus, and even speak and understand others. MS almost always causes other issues, too.

Other signs of MS include:

If you have brain fog and other symptoms of MS, talk to your doctor. There’s no cure for the condition, but medication can improve symptoms, speed up recovery from attacks, and slow the progress of the disease.

Underactive Thyroid

Your thyroid gland is a butterfly-shaped organ located in your neck. If it doesn’t produce enough thyroid hormones, many parts of your body, including your brain, may not function as quickly or efficiently as usual. That can lead to forgetfulness and trouble thinking clearly.

If your thyroid is the problem, you might also:

  • Feel very tired
  • Gain weight for no apparent reason
  • Feel weak, stiff, or sore in your muscles
  • Have less tolerance for cold
  • Become constipated

If you think you have hypothyroidism, see your doctor. A daily pill can replace the hormones that your thyroid doesn’t make.

Chronic Fatigue Syndrome

Brain fog is a constant problem for most people with chronic fatigue syndrome. Doctors diagnose this condition after you have at least six months of physical and mental fatigue. Experts still aren’t sure what causes it, but problems with memory, focus, and thinking are symptoms.

Other signs include:

There’s no cure for chronic fatigue. But if you see a doctor, she can offer treatments for your symptoms that may include brain training and specialized physical exercises.


Like chronic fatigue syndrome, fibromyalgia is a condition that causes mental and physical exhaustion. And like with chronic fatigue, experts don’t entirely understand what causes it. But, ‘fibro-fog” is one of the main symptoms of this condition.

Other symptoms include:

If you think you have fibromyalgia, see your doctor. She cannot provide a cure, but a combination of medications and lifestyle changes can help you improve and manage your symptoms.

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Fiona Gupta, MD, director of wellness and health in the department of neurosurgery at the Icahn School of Medicine at Mount Sinai, New York.

Mary Jane Minkin, MD, professor of obstetrics, gynecology, and reproductive sciences at Yale University School of Medicine, New Haven, CT.

University Hospital Network/Princess Margaret Cancer Foundation CA: “Cancer Related Brain Fog.”

Arthritis Foundation: “Fibro Fog.”

Harvard Health Letter: “Sharpen Thinking Skills With a Better Night's Sleep,” “Is an Underlying Condition Causing Your Fuzzy Thinking,” “Vitamin B12 deficiency can be sneaky, harmful.”

Mayo Clinic: “Does ‘baby brain’ really exist?” “Obstructive Sleep Apnea,” “Hypothyroidism (underactive thyroid),” “Chronic Fatigue Syndrome,” “Fibromyalgia.” Frontiers in Physiology: “Caught in the Thickness of Brain Fog: Exploring the Cognitive Symptoms of Chronic Fatigue Syndrome.”

National Multiple Sclerosis Society: “Cognitive Changes,” “What is MS?” “MS Symptoms.”

Journal of Neuroscience: “Impact of Sex and Menopausal Status on Episodic Memory Circuitry in Early Midlife.”

American Journal of Epidemiology: “Menopause-associated Symptoms and Cognitive Performance: Results from the Study of Women's Health Across the Nation.”