Even a mild case of COVID can cause brain changes. It's too soon to know if the damage lasts.

A new study provides the most conclusive evidence yet that COVID-19 can damage the brain, even in people who weren't severely ill.

The study, published Monday in "Nature," used before-and-after brain images of 785 British people, ages 51 to 81, to look for any changes. About half the participants contracted COVID-19 between the scans – mostly when the alpha variant was circulating – which left many people at least temporarily without a sense of smell.

Analysis of the "before" and "after" images from the UK Biobank showed that people infected with COVID-19 had a greater reduction in their brain volumes overall and performed worse on cognitive tests than those who had not been infected.