What is long COVID brain fog—and can it be cleared?

While most people recover fully from COVID, about 8 percent of those infected develop “Long COVID,” or lingering symptoms that they didn’t have before, according to a survey published in JAMA Network Open in 2024. Those in this minority continue to have issues weeks, months, or even years later. One of the most common persistent symptoms of Long COVID: brain fog.

“COVID brain fog is a real syndrome with biological explanations and people are not alone in experiencing it,” says Shelli Kesler, PhD, a cognitive neuroscientist 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, explains Kesler. “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,” she 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 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 believe that most of the damage comes from indirect effects of COVID infection, such as inflammation that harms brain cells. Certain other viruses like HIV and Epstein Barr (the virus that causes mononucleosis) may cause brain fog in this way. Some experts have observed that Long COVID brain fog resembles “chemo brain,” or mental cloudiness related to inflammation caused by cancer treatment or some types of cancers.

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 medication side effects, insomnia, stress, or an underlying condition such as diabetes, lupus, or fibromyalgia. 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

“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 Long COVID may cause brain fog in some people and not others. While anyone can develop Long COVID, studies suggest that it disproportionately affects people who have had a severe case of COVID or who have other health conditions, such as diabetes or lung disease.

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 attention problems and fatigue may receive a short course of psychostimulants. Other therapies may include:

• Antidepressants for depression
• Anxiolytics for anxiety
• Psychotherapy
• 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.

If symptoms persist or interfere with daily functioning, see a healthcare provider (HCP), who may suggest a neuropsychological evaluation (to assess your ability to think, behavior, and mood or personality), and refer 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.