The pandemic’s effects on teenagers were profound — numerous studies have documented reports of issues with their mental health, social lives and more.

Now, a new study suggests those phenomena caused some adolescents’ brains to age much faster than they normally would — 4.2 years faster in girls and 1.4 years faster in boys on average, according to the study published Monday in the journal Proceedings of the National Academy of Sciences.

By being the first to contribute details on aging differences by sex, the study adds to the existing body of knowledge provided by two previous studies on the Covid-19 pandemic and accelerated brain aging among adolescents.