A group of scientists from the UK published the results of a large-scale study in the medical journal The Lancet, which unequivocally indicate the negative impact of coronavirus on the level of intelligence. According to researchers, it persists after recovery from Covid-19.

• Suspicions concerning neurological complications after Covid-19 have been expressed for a long time - many patients who have been ill complain of prolonged "fog in the head", problems with memory and attention, headache and depression, and other signs of damage to the central nervous system.
• One of the characteristic symptoms of Covid-19 - the loss of smell and taste - is also associated with disturbances in the functioning of the central nervous system: the coronavirus damages the olfactory neurons in the brain.
• However, there has not yet been reliable evidence of the effect of SARS-CoV-2 on intelligence, despite the fact that coronavirus has already been found in certain areas of the brain of those who died from Covid-19.
• Experts from British universities, with the help of the BBC, conducted a questionnaire online survey of mental abilities, which took place from January to December 2020 and qualitatively covered 81,337 people - so many people provided all the required data.
• The study included the Great British Intelligence Test cognitive tests, using a different and more accurate method than IQ tests, as well as a questionnaire on the topic of Covid-19 - whether there was an official diagnosis, what symptoms manifested, was treated at home or in a hospital, how bad the course was. illness, whether psychological problems now bother.
• Scientists compared the results of people who suffered from Covid-19 with those of healthy people, taking into account gender, age, race, income level and education, and other indicators. A sample of 81,000 people was more than enough to level out any individual differences using statistical methods.
• Scientists also weeded out the influence on the intelligence of pre-disease factors such as gender, age, profession, country of residence using a more general model, which was based on an independent GBIT dataset collected from 269,264 people.
• As a result, the study revealed significant signs of deterioration in intelligence due to the transferred Covid-19. The most serious damage the coronavirus has inflicted on people who have had a severe form with the use of mechanical ventilation - their global aggregate intelligence score decreased by 0.47 SD, which is approximately seven traditional IQ points.
• In people who required hospitalization without the use of mechanical ventilation, the level of intelligence fell by 0.26 SD. Those who got sick at home with a mild form of Covid-19 lost a total of 0.23 SD. For comparison, a stroke leads to an average deterioration in intelligence of 0.24 SD.
• The greatest damage the coronavirus inflicts on the ability to abstract logical reasoning, planning and concentration. The ability to work with flat and three-dimensional objects is noticeably deteriorating.
• The researchers also examined the possible link between cognitive impairment and the time that has passed since the illness. They analyzed a subset of people who were tested at different times after the first symptoms of Covid-19 were detected - from a few weeks to nine months. Scientists have not found any pattern - this means that the intellect affected by the coronavirus does not recover over time.

https://www.thelancet.com/journals/eclinm/article/PIIS2589-5370(21)00324-2/fulltext