Two years after recovering from COVID-19, people of all ages have greater risk of brain challenges like dementia, psychosis, epilepsy and brain fog.

That’s according to a study involving more than 1 million people conducted by the University of Oxford. Published in the journal The Lancet Psychiatry, the study relied on health data from more than 1 million people — mostly from the United States, but also from Australia, the United Kingdom, Spain, Bulgaria, India, Malaysia and Taiwan. The data came from an international network called TriNetX that removes identifying information.

The researchers compared patients of all ages who’d been diagnosed with COVID-19 against a matched set of patients who’d had other respiratory infections. Then they assessed the risk of developing 14 different neurological and psychiatric diagnoses.

“It is good news that the excess of depression and anxiety diagnoses after COVID-19 is short-lived, and that it is not observed in children. However, it is worrying that some other disorders, such as dementia and seizures, continue to be more likely diagnosed after COVID-19, even two years later,” said Paul Harrison, a professor in Oxford’s Department of Psychiatry and a researcher at the National Institute for Health and Care Research’s Oxford Health Biomedical Research Centre, in a news release.

“It also appears that omicron, although less severe in the acute illness, is followed by comparable rates of these diagnoses,” he added.

Said Max Taquet, an academic clinical fellow at Oxford and the study’s lead author, “The findings shed new light on the longer-term mental and brain health consequences for people following COVID-19 infection. The results have implications for patients and health services and highlight the need for more research to understand why this happens after COVID-19, and what can be done to prevent these disorders from occurring, or treat them when they do.” 

The average age in the study was 42.5 years, and 58% of those included were female.

The Washington Post reported that adults are especially challenged by brain fog. And it noted that the share of older adults who developed dementia within the two years after being infected with COVID-19 — 4.5% compared to 3.3% of those following other respiratory illnesses — was “particularly worrisome” to the researchers, given how devastating a dementia diagnosis is.

The study “allows us to see without a doubt the emergence of significant neuropsychiatric sequelae in individuals that had COVID and far more frequently than those that did not,” David Putrino, director of rehabilitation innovation at Mount Sinai Health System in New York, told The Washington Post.

Children and adults

Children had no increased risk of depression or anxiety sparked by COVID-19. And in adults, coronavirus-related depression and anxiety didn’t last. And it was no more likely than after other respiratory illnesses.

The study found that kids, however, did have an increased risk of cognitive deficit (the formal term for brain fog), insomnia, brain bleeding, ischaemic stroke, seizures and psychotic disorders, and other neurological challenges — similar to adults. But unlike adults, brain fog returned to normal after a while.

Researchers also noted that a “sizeable portion” of older adults who were diagnosed with neurological or psychiatric challenges died, especially those who had dementia, epilepsy or seizures.

The research found neurologic and psychiatric disorders were more often seen during the delta variant wave and omicron wave than during the alpha wave of COVID-19. “Participants who had been infected with the delta variant had an increased risk for ischaemic stroke, cognitive deficit, insomnia, anxiety disorders, and epilepsy or seizures when compared to participants who had been infected with the alpha variant,” as Medical News Today reported.

And though death rates from the omicron variant of COVID-19 were lower than with the delta variant, the risk of developing psychiatric or neurological problems did not decrease but remained similar to that posed by the delta variant even two years later.

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Among study limitations, the researchers noted that how severe or long-lasting the disorders are is not known. And they couldn’t say how long the conditions were present before being diagnosed. Additionally, “unrecorded cases of COVID-19 and unrecorded vaccinations introduce some uncertainty into the results,” they wrote.

The Washington Post listed another limitation: “The study’s reliance on a trove of de-identified electronic health data raised some cautions, particularly considering the tumultuous time of the pandemic. Tracking long-term outcomes may be hard when patients may have sought care through many different health systems, including some outside the TriNetX network.”

Earlier findings

Previous research by the same group found “substantial” neurological and psychiatric illness in the six months after COVID-19 infection. The greatest risk was for those with severe COVID-19 symptoms, but others were impacted, too.

Stanford University researchers also recently published findings regarding brain fog. In June, they noted that COVID-19 brain fog is “biologically similar to cognitive impairment caused by cancer chemotherapy, something doctors often refer to as ‘chemo brain.’ In both cases, excessive inflammation damages the same brain cells and processes,” they wrote.

The impact can be seen, according to the study, which was published in the journal Cell, with “even mild respiratory infection,” creating what it called “persistent” brain inflammation that interferes with the regulation of brain cells that are important to healthy brain function.