Catching Covid has made people less intelligent – with severe infections reducing IQ the most, new study suggests

Catching Covid makes people less intelligent, with severe infections reducing IQ the most, a study suggests.

Britons who avoided the disease typically did the best in intelligence tests, while those who ended up in hospital scored the worst.

But even those who suffered only mild illness are likely to have had their cognitive abilities decline, it is believed.

Researchers from Imperial College London analyzed data on more than 112,000 volunteers who took Covid tests during the pandemic.

Analysis revealed that those admitted to intensive care with Covid scored around nine IQ points lower on average in exams than those who avoided infection.

Those who reported having long-term Covid – persistent symptoms such as ‘brain fog’ – scored six points lower and those with only mild infection two points lower.

Professor Adam Hampshire, lead author of the study published in The Lancet medical journal, tried to match people as closely as possible when comparing the groups in an attempt to account for other factors.

Additional studies found long-lasting cognitive effects, even in people who were infected a year or more earlier.

The original Covid strain was associated with a greater decrease in IQ, while there were only marginal differences with Omicron. Vaccination also appeared to have a protective effect.

Professor Hampshire said the implications of the figures are “quite frightening”.

The participants had signed up to Imperial College’s React study. Dr. Taquet said the results should be interpreted with caution since the study did not compare the same person before and after infection.

Professor Benedict Michael, director of the University of Liverpool’s infectious neuroscience laboratory, said there is “clearly a very hard-hit group”.

But he added: ‘I have yet to see convincing evidence that the vast majority of the population has been knocked back by X number of IQ points.’

Separate studies analyzing brain scans taken before and after the pandemic suggest that Covid infection can have an impact even in those who had not been hospitalized.

Professor Michael said it did not appear to be the virus infecting the brain, but a secondary consequence of infection elsewhere in the body – potentially acting on blood vessels and reducing oxygen supply. Researchers say it remains unclear whether the brains of Covid patients will fully recover.