Teen Girls’ Brains Aged Rapidly During Pandemic, Study Finds
Neuroimaging found girls experienced cortical thinning far faster than boys did during the first year of Covid lockdowns.
By Ellen Barry
Sept. 9, 2024, 3:39 p.m. ET
A study of adolescent brain development that tested children before and after coronavirus pandemic lockdowns in the United States found that girls’ brains aged far faster than expected, something the researchers attributed to social isolation.
The study from the University of Washington, published on Monday in the Proceedings of the National Academy of Sciences, measured cortical thinning, a process that starts in either late childhood or early adolescence, as the brain begins to prune redundant synapses and shrink its outer layer.
Thinning of the cortex is not necessarily bad; some scientists frame the process as the brain rewiring itself as it matures, increasing its efficiency. But the process is known to accelerate in stressful conditions, and accelerated thinning is correlated with depression and anxiety.
Scans taken in 2021, after shutdowns started to lift, showed that both boys and girls had experienced rapid cortical thinning during that period. But the effect was far more notable in girls, whose thinning had accelerated, on average, by 4.2 years ahead of what was expected; the thinning in boys’ brains had accelerated 1.4 years ahead of what was expected.
“That is a stunning difference,” said Patricia K. Kuhl, a director of the Institute for Learning and Brain Sciences at the University of Washington and one of the study’s authors. The results, she added, suggested that “a girl who came in at 11, and then returned to the lab at age 14, now has a brain that looks like an 18-year-old’s.”
Dr. Kuhl attributed the change to “social deprivation caused by the pandemic,” which she suggested had hit adolescent girls harder because they are more dependent on social interaction — in particular, talking through problems with friends — as a way to release stress.
The difference between the genders “is just as clear as night and day,” Dr. Kuhl said. “In the girls, the effects were all over the brain — all the lobes, both hemispheres.”
There has been ample evidence of a deterioration in the well-being of teenagers during the pandemic, but the study contributes something new to this discussion: physical evidence.
Researchers described the finding as striking, but cautioned against assuming that the accelerated cortical thinning is a sign of damage.
“Thinning is not a problem, it is actually a sign of maturational change,” said Ronald E. Dahl, who directs the Institute of Human Development at the University of California, Berkeley and was not involved in the study. “Accelerated thinning is being interpreted as problematic, and it could be, but that is a leap. ”
The researchers began with a cohort of 160 children and adolescents, with the goal of characterizing typical changes during the teenage years. They took their first measurements in 2018, when their subjects ranged in age from 9 to 17. But pandemic shutdowns prevented them from collecting a second wave of data in 2020.
By 2021, all their subjects were emerging from a period of prolonged stress, creating what Neva Corrigan, a research scientist and the study’s lead author, described as “a natural experiment.” Around 130 of the subjects returned for a second round of testing, which the team compared with a model that predicted typical brain development in adolescence.
Though several previous brain studies had found that the stress of the pandemic accelerated cortical thinning, none had compared the changes in boys and girls.
“We were just blown away by the significance of the effects that we found,” Dr. Corrigan said. “The results weren’t subtle. It’s not like we were looking at small changes that were barely there. It was a dramatic shift post-Covid.”
The accelerated cortical thinning occurred all over girls’ brains, in 30 different regions, but was most pronounced in the bilateral fusiform, which helps recognize faces and facial expressions; the left insula, which helps with processing emotions; and the superior temporal gyrus, which is critical for language comprehension. By contrast, accelerated cortical thinning was found in only two regions in boys’ brains, both involved in visual processing.
The researchers said it was not clear whether the changes were permanent, or whether, with the restoration of normal social interactions, the teens’ brain development would return to a typical rate.
“Let’s say that girl who comes back at age 14,” Dr. Kuhl said. “Let’s say her whole life gets better as the pandemic recedes, her social life returns and she’s back with her friends. All the stress hasn’t been removed, but at least she’s got that release valve.”
Bradley S. Peterson, a pediatric psychiatrist and brain researcher who was not involved in the study, noted that the pre- and post-pandemic brain data came from different subsets of the cohort, so the results do not measure change in cortical thickness in a single group.
He said it was unclear whether the changes in brain development could be attributed to the social isolation of the lockdown, rather than “any other of a vast number of experiences” that occurred during that period, among them a rise in screen time, an increased use of social media, less physical activity, less classroom time and more family stress.
And like Dr. Dahl, he cautioned against framing the changes as pathological. In otherwise healthy young people, the thinning of the cortex “is thought to represent the brain reshaping itself adaptively according to the needs of experience.”
An acceleration of that process during the lockdown, if it did occur, “could in fact represent nature’s adaptive response in the brain that conferred greater emotional, cognitive and social resilience,” he said.
