Previous research has identified the negative effects of the pandemic on young adults' mental health. Now a new study shows it not only changed their brains in an emotional and behavioral capacity, but also physically.
The study, published Monday in Proceedings of the National Academy of Sciences, found the brains of adolescents matured at an unusually accelerated rate as a result of the pandemic, with girls' brains appearing an average of 4.2 years older than expected and boys' 1.4 years.
Brain age is measured by the thickness of the cerebral cortex, the outer layer of tissue in the brain that peaks in childhood and thins from then on. Researchers from the University of Washington noted in the study that chronic stress and adversity can accelerate the cortex's thinning, which is linked to an increased risk for mental and behavioral disorders like anxiety, depression and stress — which were reported at higher levels in teens during the pandemic, most notably in girls.
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In 2018, the UW researchers scanned 160 brains of participants aged 9 to 17 aiming to track general brain structure changes over time, but after they were unable to return for a second scan in 2020 due to the pandemic, the researchers changed their objective. When over 80% of the participants returned for the second scan in 2021, the researchers instead used a model of expected cortical thinning created from the 2018 data to track the teens' brain-maturation levels.
Results showed accelerated thinning across the adolescents. However, female brains showed cortical thinning in all lobes and both hemispheres, with the most accelerated changes in cognitive areas linked to processing faces, emotional experiences and language. In boys, these effects were only found in the visual cortex.
Patricia Kuhl, senior author and co-director of the University of Washington Institute for Learning & Brain Sciences, noted the female versus male brain maturation differences could be because girls rely more heavily on social interactions and emotional relationships with other girls, while boys gather more for physical activities. This would've led girls to suffer more from the isolation brought on by the pandemic, and thus their brains were affected more dramatically.
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"Teenagers really are walking a tightrope, trying to get their lives together," Kuhl said. "They’re under tremendous pressure. Then a global pandemic strikes and their normal channels of stress release are gone. Those release outlets aren't there anymore, but the social criticisms and pressures remain because of social media. What the pandemic really seems to have done is to isolate girls."
The effects of premature brain aging in teens are unclear, but in older populations, the cerebral cortex's level of thinning correlates with cognitive functions like processing speed and ability to complete tasks. And with the cerebral cortex unlikely to regain its thickness — though slowing the thinning over time could be possible — the UW researchers say additional studies are necessary to fully grasp how to handle the shift.
"The pandemic provided a test case for the fragility of teenagers' brains," Kuhl said. "Our research introduces a new set of questions about what it means to speed up the aging process in the brain. All the best research raises profound new questions, and I think that's what we've done here."
