COVID-19 Increases Risk of Brain Conditions for 2 Years After Infection, Study Finds

People who have been infected with COVID-19 are at an elevated risk of developing certain brain disorders for as long as two years after the infection, according to a new study conducted by the University of Oxford.

In a report published in The Lancet Psychiatry, researchers analyzed the health records of more than 1 million people who had recovered from acute COVID-19 to understand whether they were more likely to be diagnosed with a neurological or psychiatric disorder than those sick with other respiratory conditions.

The increased odds that people who had COVID-19 would develop some common psychiatric disorders and mood disorders—like anxiety and depression—diminished after a few months. But this group remained at relatively high risk for dementia, epilepsy, psychosis, and brain fog two years after their COVID-19 infection.

Even those who got sick during the Omicron wave were at higher risk of these conditions, despite that variant’s tendency to cause milder acute illness.

About one in five people who have had COVID-19 report still experiencing symptoms of long COVID, according to recent data.

The researchers emphasized that this isn’t technically a long COVID study, because they weren’t able to verify that the patients’ diagnoses were directly caused by COVID infections. Nevertheless, it helps scientists understand how COVID-19 is associated with different outcomes than other respiratory illnesses.

Following patients for such a long period makes this study particularly valuable, said Laura Chambers, MPH, PhD, an epidemiologist and cofounder of the Long COVID Initiative at Brown University, who wasn’t involved in the study.

“This is important for our public health messaging and our health system preparedness, in terms of anticipating clinical and other supportive services that will need to be available,” Chambers said.

Increased Diagnoses of Neurological and Psychiatric Disorders

The researchers identified a group of almost 1.3 million people who had been diagnosed with COVID-19 from a set of about 89 million patients from the TriNetX electronic health records system. Most of the patients were treated in the United States, with some in Australia, the United Kingdom, Bulgaria, Spain, India, Malaysia, and Taiwan.

The researchers identified patients infected with COVID-19 between January 2020 and April 2022 and matched them with people who had other respiratory diseases during the same period based on vaccination status and demographics.

About a third of those who had a COVID-19 infection were diagnosed with a psychiatric or neurological condition within 6 months. For 13% of these people, it was their first recorded diagnosis of this type.

The most common diagnoses immediately after a COVID-19 infection were anxiety and mood disorders. But two months after recovery, patients were no more likely to develop anxiety and depression than those who recovered from different respiratory illnesses.

There was a 1.2% difference in the number of older adults who developed dementia after COVID-19 compared to those who were COVID-free. The risk difference for developing ischemic stroke in these groups was 0.3%.

These figures may seem small, but even a slightly increased risk for serious disorders that affect the nervous system can have a big impact, according to Paul Harrison, MA, BM, BCh, DM (Oxon), a professor of psychiatry at the University of Oxford and lead author of the study.

“Although the individual risks for most disorders are small, the effect across the whole population may be substantial for health and social care systems due to the scale of the pandemic and that many of these conditions are chronic,” Harrison said in a statement. “As a result, healthcare systems need to be resourced to deal with the anticipated need, both within primary and secondary care services.”

The researchers reported data on children and adults 65 years and older separately. The risk of developing lasting neurological and psychiatric disorders was the highest among older adults compared to other age groups.

Like adults, children were more likely to be diagnosed with brain fog, insomnia, brain bleeding, seizures, psychosis, and other neurologic conditions after COVID-19.

The risk for epilepsy was higher among children than adults over the long term. However, the children were not found to be at greater risk of anxiety and depression than those who recovered from other respiratory infections, and the increased risk of neurologic and psychiatric diagnoses diminished more quickly than in adults.

Mild Infections Don’t Necessarily Mean a Lower Risk of Brain Conditions

The study compared data across various waves of the pandemic. People who caught COVID-19 during the Alpha wave tended to have the lowest increase in risk for neurologic and psychiatric problems.

A slew of studies indicated that Omicron causes milder acute illness and is less likely to result in death than Delta. Chambers, who has been researching long COVID, said many people had hoped that the long-term impact of COVID-19 would be lower if Omicron infections were less severe.

However, those who got sick while the Omicron variant was dominant saw the same long-term risks as those during the Delta wave, according to the new study.

The findings suggested that even if future variants evolve to cause milder acute illness, the health system must be prepared to support people who experience mental health and nervous system challenges, she said.

Next Up: Understanding How COVID-19 Harms the Brain

This study does not tease out why COVID-19 impairs the brain.

“The study cannot reveal the mechanisms involved but does point to the need for urgent research to identify these, with a view to preventing or treating them,” Max Taquet, PhD, a senior research fellow at Oxford and lead author of the study, said in the statement.

Other studies have found that COVID-19 infections can cause changes in brain structure and function.

In one recent study, researchers conducted brain scans of adults about four months after a COVID-19 infection and found that many of them experienced changes to their brain structure and faster cognitive decline.

Additionally, it’s still unknown just how severe and long-lasting these conditions are. Future research might look into how greatly post-COVID-19 brain disorders impact one’s ability to function well in their daily lives, Chambers said.

This data only reflects the experiences of people who went to the doctor when they were sick with COVID-19, or to assess the symptoms that linger. That leaves researchers in the dark about outcomes for people who are asymptomatic or don’t seek health care when sick with COVID-19.

“You’re kind of limited to the people presenting to the healthcare system—you only have information on their health from the times when they do seek clinical care,” Chambers said. “There are a lot of unknowns about how to support people when they do present for care, but there are also important concerns about the people who are likely experiencing persistent symptoms but aren’t presenting for care.”

While researchers continue to tease out what happens in the brain and body after a COVID-19 infection, Chambers said it’s helpful for health providers to have these outcomes on their radars.

“Increased risk is important for patients to be aware of and for clinicians to be aware of as patients are navigating their symptoms and trying to understand management approaches and kind of the underlying causes,” Chambers said.