On variants, the risk of neuropsychiatric diagnoses rose, from 10% higher for anxiety to 38% for brain fog — after the Delta variant emerged than after the alpha version. Similar risks continued with Omicron, even though that variant has milder effects during the acute phase of infection.

“What these data show in this very large cohort retrospectively analyzed is that the mood disorders and anxiety problems that are really, really prevalent in long Covid tended to resolve in a matter of months, which is great news for patients with long Covid who are not used to suffering in those ways,” Wes Ely, a critical care physician at Vanderbilt University Medical Center and associate director for research for the VA Tennessee Valley Geriatric Research and Education Clinical Center, told STAT. He was not involved in the Oxford studies.

“The other finding of this fascinating investigation is that the cognitive problems, the neurocognitive deficits that make people have brain fog, do not resolve so quickly,” he said. “Clinically, in my own practice and in our long Covid clinic, this is exactly what we’re seeing: that the acquired dementia that these patients get tends to be lasting and very problematic.”