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What Causes Brain Fog?

07 September 2021

Those times when you scurried around the house looking for your misplaced keys or scratched your head in front of the refrigerator for a minute without knowing what you were there for don’t happen by accident. No, you don’t have Alzheimer’s disease or dementia. No, you aren’t losing your mind. Instead, you may be experiencing something called brain fog.

Knowing what brain fog is and what causes it are the first steps in returning to mental clarity. We outline common brain fog symptoms to be aware of, what you can do to remedy it and how it has become more prevalent during the COVID-19 pandemic.

What does brain fog mean?

Brain fog is a term, rather than a medical condition, used to describe symptoms or side effects caused by an underlying factor or condition. The term comes from cognitive impairment, also known as cog-fog, which affects how a person makes decisions, remembers things, learns things and concentrates.

The brain is a complex organ composed of billions of neurons that require energy. With so many moving parts, it’s not surprising the brain prefers a routine. These repetitive patterns — waking up, going to work or school and then going to sleep — help the brain function smoothly and efficiently as you go about your day. While these patterns may go unnoticed, we need them to keep the brain from becoming overwhelmed.

The Limbic system, which is on either side of the thalamus, is the part of the brain involved in emotional or behavioral responses. The most well-known response is the fight-or-flight reaction, which is the brain’s way of handling emotions.

When you become overly stressed, fatigued or experience hormonal changes that cause emotions to run high, the limbic system can get in the way of the part of the brain responsible for making executive functions. 

At a high level, executive functions are the cognitive skills your brain uses to coordinate organizational (paying attention, planning tasks, thinking and problem solving) and regulatory (regulating emotions, moral reasoning and making decisions) abilities. As a result, the external factors impact how the brain focuses and carries out routine communications such as focusing on a conversation or forgetting a word while speaking.

What can cause brain fog?

Since brain fog occurs when the brain becomes overwhelmed and is unable to complete normal tasks, the causes tend to be wide ranging.

The following are common causes of brain fog. Many of these factors are directly related and often become cyclical. In other words, stress can lead to poor sleep hygiene and depression just as depression can lead to trouble sleeping. People with anxiety or depression are often more stressed and have trouble sleeping.

Hormonal changes

Brain fog caused by hormonal changes can result from menopause, pregnancy or thyroid problems. For example, progesterone and estrogen levels increase when you’re pregnant, which can affect your memory. In menopause, women can experience lower levels of estradiol, a form of estrogen produced by the ovaries. This can cloud your thinking and result in poor concentration. 

Mental health issues 

The more energy the brain uses to combat anxiety and depression, the less energy it has to devote toward routine tasks. Therefore, many people who live with depression claim they’re mentally exhausted. It also explains why anxiety can sometimes be misdiagnosed as attention deficit hyperactivity disorder. The anxiety takes away from the brain’s natural ability to carry out executive functions, resulting in symptoms that mimic ADHD. 

Neurological disorders

Neurological disorders, such as multiple sclerosis, impact how your brain communicates with other organs in your body. About 50 percent of people with multiple sclerosis have issues with memory, attention to detail or handling tasks.


The fight-or-flight response triggered by stress isn’t always negative. The sense of alertness is what allows you to quickly hit the breaks or swerve to avoid an accident. Stress becomes a problem when it turns excessive, causing the brain to pump out cortisol, adrenaline and norepinephrine. The presence of these stress hormones tires out the brain and leads to fatigue.

Poor sleep hygiene

Once you wake up and go about your day, your body produces adenosine, a neurotransmitter that helps initiate the sleep cycle. The more adenosine produced, the more tired you become. The adenosine is then removed during sleep, although this chemical can remain if you don’t rest long enough. The result is a constant drowsy feeling that can lead to brain fog. 

Vitamin B12 deficiency

Vitamin B12 is key for cellular health, mainly nerve cells and red blood cells. A deficiency in this important vitamin, which is found in animal products such as beef, chicken, pork and seafood, can impact your memory. Vegetarians and vegans may be more prone to B12-related brain fog since they don’t eat animal products.

What does brain fog feel like?

In nature, fog decreases visibility and obscures what you’re able to see. The same concept applies to the brain — certain factors can lead to a state of confusion or obscurity. Aside from confusion, you may also feel fatigued, sluggish or generally just not like yourself. Others who experience brain fog claim they are disoriented, distracted and more prone to forget about simple tasks they’re accustomed to completing. 

In conversations, brain fog may cause you to stumble on your words or cause you to forget a word in a sentence. It can also cause you to lose your train of thought, like gazing into the refrigerator only to forget what you meant to take out.

How to cure brain fog

A “cure” for brain fog isn’t the correct term since it’s not a medical condition. But there are ways to limit or reduce the symptoms. It all depends on what is causing the brain fog in the first place.

Many of the first steps to take are general healthy habits everyone can benefit from — exercising, eating a well-balanced diet and getting enough sleep. Strive for fruits, vegetables and lean proteins when eating. The Mediterranean diet, which focuses on plants and seafood, has been shown to be beneficial for cognitive function.

Exercising can not only reduce stress and help your mental health, it also helps increase blood flow and nutrients to your brain. You don’t need strenuous activity, either. Try a combination of yoga and meditation to establish a positive mindset. A healthy brain is more equipped to stay on track to perform daily routines instead of being pushed to the side by brain fog.

For those struggling with sleep hygiene, shoot for eight hours of sleep per night. The extra time in bed will keep you refreshed and recharged each day. If anxiety or depression have a strong grip on your life, consider talking to a counselor or a licensed therapist to minimize stressors in your life. Here are some tips on how to prepare for your first mental health visit.

Brain fog after COVID

Americans are noticing an uptick in feeling the effects of brain fog from COVID-19. The reasons are two-fold: brain inflammation and lifestyle changes associated with the pandemic.

In general, COVID restrictions, travel guidelines and social distancing efforts have all disruptive routines. Even work routines are different with many people working from home on a permanent basis. A break in routine, coupled with isolation, lack of exercise and added stress, is a perfect recipe for brain fog.

Brain fog is a common long-haul COVID symptom. For people who have contracted COVID, the virus itself creates an inflammatory response in the immune system and other organs such as the lungs and brain. This response can alter the way the brain communicates, thus leading to brain fog. 

In fact, one study found cognitive impairments were present in patients who recovered from COVID.


If you or a loved one is experiencing brain fog, either from COVID-19 or other causes, contact your primary care physician to schedule an appointment and undergo further evaluation. 


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