COVID-19 Lockdowns May Have Prematurely Aged Teenagers' Brains

COVID-19 lockdowns saved lives during the pandemic, with research indicating that they prevented about 1 million deaths in the US alone during the first six months of 2020.

Yet restricting people to their homes and local areas also transformed daily life, frequently with harmful consequences. As well as causing severe economic disruption, COVID lockdowns separated people of every age from schools, workplaces and other social settings, leaving many isolated and lonely.

Children were particularly badly affected. Although the full consequences are still uncertain, research suggests that teenagers were especially susceptible to this social disruption.

A new study now indicates that the pandemic may have prematurely aged teenagers' brains by accelerating the natural thinning of the cerebral cortex that happens as people grow older. The impact appeared particularly marked in girls.

"We think of the COVID-19 pandemic as a health crisis, but we know that it produced other profound changes in our lives, especially for teenagers," says senior author Patricia Kuhl, co-director at the University of Washington's Institute for Learning & Brain Sciences (I-LABS).

COVID-19 lockdowns and teenage brain development

Kuhl and her colleagues began the study in 2018, originally intending it to be a longitudinal investigation into normal changes in the developing teenage brain.

The researchers note that the cerebral cortex becomes naturally thinner as people age, including during adolescence, and that cortical thickness can indicate overall brain maturation.

In 2018, the team gathered MRI data from 160 children aged between 9 and 17. They planned to collect further data from the same participants in 2020, but COVID disrupted those plans, as it did for so many others that year.

Follow-up testing was postponed until 2021. This effectively brought the original study to an end, while also leaving the researchers with pre-pandemic data that could show how lockdowns had affected the children, some of whom had reached adulthood since 2018.

"Once the pandemic was underway, we started to think about which brain measures would allow us to estimate what the pandemic lockdown had done to the brain," says Neva Corrigan, lead author and research scientist at I-LABS.

"What did it mean for our teens to be at home rather than in their social groups – not at school, not playing sports, not hanging out?" Corrigan says.

Faster cortical thinning in teenage girls

Corrigan and her colleagues explain that previous research has linked chronic stress and adversity with faster thinning of the cerebral cortex. This process is associated with a greater risk of neuropsychiatric and behavioural disorders, including anxiety and depression.

The researchers write that their new study reproduces findings from two earlier papers, both of which identified more rapid cortical thinning in teenagers after 2020.

As well as providing further evidence of a connection with lockdowns, the authors uncovered a new finding: pandemic-era cortical thinning was more severe in girls.

Using the data collected in 2018, the team created a model predicting the cortical thinning expected in the years after the participants' first MRI scans. They then carried out new MRI examinations of the same group, with more than 80 percent returning for the post-pandemic follow-up.

According to the authors, the new MRI scans revealed accelerated cortical thinning throughout adolescence. The effect was especially strong in female participants, whose brains appeared to be affected more extensively.

Among male participants, thinning was confined to the visual cortex. In female participants, however, it was much more widespread, occurring across every lobe and in both hemispheres.

To give the results context, the researchers also calculated how many years would normally be needed for the same amount of cortical thinning to take place.

The study found that, for males, the average acceleration in cortical thinning from 2018 to 2021 matched an additional 1.4 years. While substantial, that was far smaller than the effect observed in females, for whom the average acceleration equated to an extra 4.2 years of brain ageing.

"Teenagers really are walking a tightrope, trying to get their lives together," Kuhl says. "They're under tremendous pressure. Then a global pandemic strikes and their normal channels of stress release are gone."

Kuhl adds that, despite losing many sources of stress relief in 2020, teenagers were still exposed to social pressure and cyberbullying through social media.

Why the effects may differ between males and females

Why lockdowns affected males and females so differently is not yet known, although Kuhl and her colleagues suggest it could relate to different social priorities.

"For females, peer relationships are of vital importance for the development of self-identity, and females rely on these relationships for emotional support more than males," the researchers write.

For teenage boys, they add, peer relationships are characterised more by "companionship and shared activities" than emotional support.

"What the pandemic really seems to have done is to isolate girls," Kuhl says. "All teenagers got isolated, but girls suffered more. It affected their brains much more dramatically."

The researchers say further work is required both to account for these differences and to investigate whether recovery is possible. It is unlikely that anyone's cerebral cortex will restore the thickness lost in 2020, but the rate of thinning may perhaps have slowed.

"The pandemic provided a test case for the fragility of teenagers' brains," Kuhl says. "Our research introduces a new set of questions about what it means to speed up the aging process in the brain."

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