According to a study published in the journal Brain, Behavior, and Immunity-Health, long-term COVID is linked to lower brain oxygen levels, poorer performance on cognitive tests, and an increase in psychiatric symptoms like depression and anxiety.

In a lab experiment, Canadian researchers from the University of Waterloo discovered that people with symptomatic COVIDS underperformed on two computer tasks. One was measuring inhibition, and another was impulsive decision-making.

The researchers observed that those who were infected did not exhibit an increase in oxygen saturation in a region of the brain that is usually active during one of the tasks, as opposed to individuals who had not been exposed to the infection. Dr. Peter Hall, lead author and researcher at the University of Waterloos Faculty of Public Health Sciences, stated that the findings of the study showed a reduced amount of oxygen absorption in the brain during a cognitive activity in the months following a symptomatic COVID-19 infection. He explained that this finding is crucial because COVID-19 is believed to affect cognitive function in the brain by depriving the brain of enough oxygen.

In a separate study, the team surveyed more than 2,000 Canadians between the ages of 18 and 56 in order to look into the connections between COVID, cognitive function, and mental symptoms. COVID patients reported having trouble focusing and displaying inhibition, as well as more severe anxiety and depressive symptoms.

The researchers also found that after adjusting for how long ago respondents were infected, these effects were still discernible and slightly stronger among unvaccinated people. 

(Source: https://www.business-standard.com/article/current-affairs/long-covid-cuts-brain-oxygen-worsens-cognitive-problems-depression-123030100400_1.html )