Lockdowns during the COVID-19 pandemic saved lives, with studies estimating that they prevented around one million deaths in the U.S. during the first half of 2020 alone. However, staying indoors for long periods had serious effects, especially on young people. Schools closed, sports stopped, and social interactions came to a halt, leaving many teenagers struggling with isolation.

Now, a new study suggests that the pandemic didn’t just affect teens emotionally—it may have physically changed their brains, making them age faster. This effect was especially noticeable in girls, researchers found.

How did the study work?

Researchers at the University of Washington started a study in 2018 to track normal brain development in teenagers. They collected MRI brain scans from 160 kids aged 9 to 17 to understand how their brains naturally change over time. However, when COVID-19 hit in 2020, the study was put on hold. The researchers later realized they could use the pre-pandemic data to compare how the brains of these teenagers developed before and after lockdowns.

In 2021, they were able to scan the brains of over 80% of the original participants. This allowed them to measure any differences in brain development caused by the pandemic.

One key finding was that the cerebral cortex—the outer layer of the brain responsible for thinking, memory, and emotions—thinned at a faster rate in teenagers during the pandemic than what is normally expected.

The cerebral cortex naturally gets thinner as people age, but for teens in the study, this process happened much more quickly than usual. Researchers compared their brain scans from 2018 and 2021 and found that lockdowns had significantly sped up the aging process of their brains.

The study found that the impact of lockdowns was much more noticeable in girls. While boys also showed faster thinning of the cerebral cortex, it was mostly limited to the visual cortex, a part of the brain that processes what we see. In girls, however, the thinning happened all over the brain, in all four lobes and both hemispheres.

To put it into numbers, boys’ brains aged about 1.4 years faster than normal, while girls’ brains aged 4.2 years faster.

Why were girls more affected?

Scientists aren’t sure why, but they have some theories. Teen girls rely on social interactions for emotional support more than boys do, the researchers explain. While boys’ friendships are often based on shared activities like playing video games or sports, girls tend to form deeper emotional connections with their friends. Losing these relationships during lockdowns may have caused more stress for them.

As senior researcher Patricia Kuhl put it, “What the pandemic really seems to have done is to isolate girls. All teenagers got isolated, but girls suffered more. It affected their brains much more dramatically.”

Scientists know that stress and hardship can speed up the aging of the brain, and this process is linked to a higher risk of anxiety, depression, and other mental health issues. Since the pandemic was a stressful time, this study suggests that lockdowns may have contributed to these problems by physically changing teenagers’ brains.

However, researchers don’t yet know if the brain can recover from this faster thinning or if the effects will last into adulthood. “Our research introduces a new set of questions about what it means to speed up the aging process in the brain,” Kuhl said.

Scientists will need to keep studying these teenagers to see if their brain aging slows down now that life has returned to normal. While the lost thickness in the cerebral cortex may not come back, it’s possible that the rate of thinning could return to a normal pace over time.

The study was published in the ​​Proceedings of the National Academy of Sciences.

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