What Is Long COVID Brain Fog—And Can It Be Cleared?

Overall, 7.5 percent of people have lingering symptoms, such as brain fog, weeks, months, or even years after recovering from COVID. Get the latest.

adult thinking and feeling tired

Medically reviewed in December 2022

Updated on December 5, 2022

As the new year approaches, the total number of confirmed COVID cases in the United States is nearing 100 million. While most people recover fully from the disease, 7.5 percent of those infected develop “long COVID,” or lingering symptoms that they didn’t have before, according to the Centers for Disease Control and Prevention (CDC). Those in this minority continue to have issues weeks, months, or even years later. One of the most common persistent symptoms: brain fog.

“COVID brain fog is a real syndrome with biological explanations and people are not alone in experiencing it,” says Shelli Kesler, PhD, director of the Brain Health Neuroscience Lab at the University of Texas at Austin.

What is it, exactly?
As the name implies, brain fog involves a range of symptoms that can affect people’s memory and executive function, or their ability to think clearly, make decisions, focus, and plan or organize tasks, explains Kesler.

One 2022 study of 72 adults who had mild to moderate COVID published in Frontiers in Psychology found that 40 percent of the participants continued to have thinking problems four months after their COVID diagnosis. And of these people who experienced lingering thinking issues, almost 1 in 4 showed problems with executive functioning. 

“Common COVID brain fog symptoms include difficulties remembering short-term information, difficulties learning new information, feeling slow in thinking and decision making, feeling indecisive, difficulty concentrating, and difficulty multitasking or attending to more than one thing at a time,” Kesler says.  

This cluster of issues can negatively affect everything from managing your finances to remembering to take your medication or being able to join in a conversation.

Why is this happening?
COVID is classified as a respiratory infection, but the virus can affect other organs in the body aside from the lungs, including the heart and the brain. In rare cases, researchers have found the virus can damage brain cells called neurons.

In one 2022 study published in Nature, British researchers analyzed the brain MRI images of people before and almost five months after they were infected with COVID. They compared these images to those of people who tested negative for the infection. The study showed that infection with COVID was associated with greater reduction in brain size, especially in parts of the brain involved in memory and executive functioning. Not all those with COVID experienced these brain-related changes, and the damage was greater for those with severe cases that required hospitalization. The researchers noted, however, that even some people with mild infections had evidence of reductions in areas of the brain tied to executive functioning. On average, the study showed declines in these regions was at most 1.8 percent.

While the virus may have possible direct effects on the brain, some researchers think that most of the damage is related to indirect effects related to COVID infection, such as inflammation that may harm brain cells. Certain other viruses like HIV and Epstein Barr (the virus that causes mononucleosis) may cause brain fog in this way. Recent research in mice also suggests that mild COVID may trigger an increase in the same inflammatory cells that cause chemo brain, or mental cloudiness that can be related to cancer treatment or to some types of cancers themselves.    

And for people who have had more severe infections, factors related to hospital stays may contribute to brain fog. One of the symptoms of post-intensive care syndrome (a combination of physical, mental, and emotional symptoms that continues after leaving the intensive care unit) is cognitive impairment, or difficulty thinking. Lack of oxygen and stroke (a relatively rare but possible complication of COVID) can also cause difficulties with thinking, particularly among those with additional risk factors, such as diabetes, high blood pressure, and high cholesterol.

Teasing out other causes of brain fog
While long COVID is a relatively new syndrome, brain fog has been around for a lot longer. It’s not a specific medical diagnosis, but healthcare professionals more commonly use the terms “cognitive dysfunction” or “cognitive deficit” to describe problems with the ability to think that can make people feel sluggish, forgetful, confused, or lacking in mental clarity. Brain fog can be related to a large range of issues, including an underlying condition, such as lupus and fibromyalgia, medication side effects, insomnia, and stress.  Other causes of brain fog can include:

  • Nutritional problems like vitamin deficiency or poor diet
  • Caffeine or nicotine withdrawal
  • Alcohol and other drugs
  • Depression, and other mental health conditions
  • Menopause and hormonal conditions like diabetes

“This overlap makes it difficult to separate COVID brain fog from effects of sleep deprivation, medication, psychiatric symptoms, and other causes, which puts people, especially women and minorities, at risk for being ignored or dismissed when presenting with brain fog symptoms,” Kesler says.

Researchers are still working to understand why COVID may cause brain fog in some people and not others, but the CDC reports that long COVID disproportionately affects people who are older, female, Hispanic, bisexual, or transgender.

Can long COVID brain fog be cleared?
Investigation into long COVID brain fog is ongoing, and there are currently no standard, evidence-based treatments for the condition. But therapy programs are already underway at some post-COVID rehabilitation centers.

Generally, treatment for brain fog depends on the particular symptoms, Kesler notes. For example, those experiencing attentions problems and fatigue may receive a short course of psychostimulants. Other therapies may include antidepressants for depression, anxiolytics for anxiety, psychotherapy, and cognitive rehabilitation, or intervention designed to improve mental processing issues related to brain injury, such as relearning certain skills or helping people develop new ones.

Since COVID brain fog may be worsened by factors like sleep problems, medication side effects, mental health conditions, or other medical problems, addressing these issues can also help, Kesler says.

Those experiencing symptoms of long COVID brain fog should make an appointment in a post-COVID rehab center if there is one available in their local area. “Many hospitals have these now,” Kesler says, noting that people can also visit their primary care physician (PCP) for guidance.

If your symptoms persist or interfere with daily functioning, see your healthcare provider (HCP), who may suggest a neuropsychological evaluation (a comprehensive evaluation that assess your ability to think, your behavior, and mood or personality), and provide a referral to a specialist, if necessary.

There are also some steps you can take at home to help ease symptoms of long COVID brain fog, including:

  • Pace yourself: Take mental and physical breaks throughout the day.
  • Focus on your nutrition. Follow a healthy, balanced Mediterranean-style diet, which may help improve brain function among other health benefits.
  • Stay active. Get regular exercise and listen to your body when it feels tired. Keep in mind that overdoing it could worsen your symptoms.
  • Prioritize sleep. Aim to get at least seven hours of sleep each night and practice good sleep hygiene, including going to bed and waking up around the same time each day.
  • Be aware of drug side effects. Avoid alcohol and unnecessary medications that may slow your thinking, such as some over-the-counter allergy medications and sleep aids.
  • Try to maintain social connections. Take part in social activities. Prioritizing your mental health and social well-being can have a range of health benefits.
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Ceban F, Ling S, Lui LMW, et al. Fatigue and cognitive impairment in Post-COVID-19 Syndrome: A systematic review and meta-analysis. Brain Behav Immun. 2022 Mar;101:93-135.
Premraj L, Kannapadi NV, Briggs J, et al. Mid and long-term neurological and neuropsychiatric manifestations of post-COVID-19 syndrome: A meta-analysis. J Neurol Sci. 2022 Mar 15;434:120162.
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