Two years after contracting Covid, diagnoses of brain fog, dementia and epilepsy are more common than after other respiratory infections, according to a study by the University of Oxford.
But anxiety and depression are not as common in adults and children, the study found.
Additional research is needed to understand how and why covid-19 leads to these conditions.
Experts say the virus is disrupting people's daily lives.
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Previous research has shown that adults are at increased risk of brain and mental health problems in the six months after a covid infection.
The study looked at the risks of 14 different disorders in 1,25 million patients two years after covid, mostly in America.
They then compared them with a group of 1,25 million people who had a different respiratory infection.
In the group that had covid, after two years there were more new cases:
- dementia, strokes and fog in adults over 65
- brain fog in adults aged 18-64
- epilepsy and psychotic disorders in children, although the overall risks were small
For example, the risk of developing epilepsy in children after Covid was 260 per 10.000, compared to 130 per 10.000 after another respiratory infection.
Their risk of developing a psychotic disorder has also increased post-covid - 18 per 10.000 - but it is still a rare condition.
Some disorders have become less common two years after covid, such as:
- anxiety and depression in children and adults
- psychotic disorders in adults
The increased risk of depression and anxiety in adults lasts less than two months before returning to normal levels, research has shown.
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"Worrying"
Professor Paul Harrison, the lead author of the study from the department of psychiatry at Oxford says that it is "worrying" that some disorders, such as dementia and strokes, are more common after covid, even two years later.
But he says the good news is that post-covid depression and anxiety are "short-lived" and have not been seen in children.
The researchers point out that it is difficult to ignore the number of those affected, but that it is "not a tsunami," and that some will likely require medical attention, which could increase the pressure on health care.
The study, published in Lancet Psychiatry (Lancet Psychiatry), did not follow individual people over two years - instead, it analyzed people with a new diagnosis two years after infection.
Nor was it considered how severe each condition was after diagnosis or how long it lasted and whether they were similar after covid compared to other infections.
They stopped calling these conditions long-term covid, although brain fog or problems with memory and concentration is a typical symptom.
A micron strain of the virus brought long symptoms of covid, a recent study showed.
Although less severe than the delta variant, omicron appears to lead to similar brain and mental health risks, the study found.
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"Social Upheaval"
The study has some limitations - it didn't look at how covid could cause brain and mental health disorders, although some experts say it could be explained by the development of micro-clots in the blood.
Dr Jonathan Rogers and Professor Glyn Lewis of University College London, who were not involved in the research, said the study highlighted some "clinical features that particularly merit further investigation" to confirm these findings.
The pandemic has changed people's lives in many different ways, says Paul Garner, emeritus professor of global health evidence synthesis at the Liverpool School of Tropical Medicine.
He adds that the small increase in the number of cases of dementia and psychosis is "probably related to the social upheavals and dystopia we are living through, and not as a direct effect of the virus".
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