If you’re among the estimated one-in-five Canadians who developed long COVID symptoms after infection with COVID-19, you might be familiar with the memory problems, focusing difficulties and a whole slew of other cognitive impairments that have become emblematic of the condition — collectively known as “brain fog.”

But despite these cognitive symptoms being present in nearly 90 per cent of long COVID cases, the biological mechanism behind why brain fog happens — and how we can treat it — has remained largely elusive. Until now.

A new paper, published in peer-reviewed journal Brain Communications, found that people living with long COVID had more significantly higher levels of a certain brain receptor than their healthy peers. The more they had, the worse their symptoms tended to get, the study suggested.