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.
“The findings are an important wake-up call about the fragility of the teenage brain,” said senior study author Dr. Patricia K. Kuhl, the Bezos Family Foundation Endowed Chair in Early Childhood Learning and codirector of the Institute for Learning and Brain Sciences at the University of Washington in Seattle, via email. “Teens need our support now more than ever.”
Significant socioemotional development occurs during adolescence, along with substantial changes to brain structure and function. The thickness of the cerebral cortex naturally peaks during childhood, steadily decreases throughout adolescence and continues to decrease through one’s lifespan, the authors wrote.
The researchers originally intended to track ordinary adolescent brain development over time, starting with MRIs the authors conducted on participants’ brains in 2018. They planned to follow up with them for another scan in 2020.
The pandemic delayed the second MRI by three to four years — when the 130 participants based in Washington state were between ages 12 and 20. The authors excluded adolescents who had been diagnosed with a developmental or psychiatric disorder or who were taking psychotropic medications.
The team used the pre-pandemic MRI data to create a “normative model” of how 68 regions of the brain would likely develop over typical adolescence, to which they could compare the post-pandemic MRI data and see if it deviated from expectations. This normative model is analogous to the normative growth charts used in pediatric offices to track height and weight in young children, the authors said. It has also been used by other researchers to study the effects of circumstances or conditions such as socioeconomic disadvantage, autism, depression, attention deficit hyperactivity disorder or traumatic stress.
The study revealed accelerated cortical thinning in the post-pandemic brains of teens — occurring in 30 brain regions across both hemispheres and all lobes for girls, and in only two regions for boys. The prevalence of the thinning amounted to 43% and 6% of the studied brain regions for girls and boys, respectively.
The study “is not a major revelation, as the authors acknowledge,” but does add to our knowledge of the subject, said Dr. Max Wiznitzer, professor of pediatrics and neurology at the Case Western Reserve University School of Medicine, via email. Wiznitzer wasn’t involved in the research.
How adversity influences the brain
The study has a few important limitations, including that senior author Kuhl contributed the study to the journal, meaning that she was also an editor of the study and able to choose, with restrictions, who peer-reviewed it.
And since everyone was affected by the pandemic, the authors didn’t have a control group, which is why they had to use normative modeling to approximate what the normal controls would have been, Wiznitzer said — “which is not as good as true controls but likely the best they can do.”
The authors also didn’t have data on participants’ families’ jobs, financial or food security or on participants’ exercise, sleep or dietary habits, they said. It’s also unknown whether the participants possibly having had Covid-19 could have contributed to the findings.
“Theirs is a good study, but even then it probably doesn’t have a large enough sample to say that the sex difference in brain aging is a reliable finding,” said Dr. Ian Gotlib, author of a 2022 study on the subject and director of the Stanford Neurodevelopment, Affect, and Psychopathology Laboratory at Stanford University, via email.
However, “after reading this paper we examined sex differences in the data we used in our study — same direction of sex differences as the authors reported, but not statistically significant with our slightly smaller sample,” added Gotlib, who wasn’t involved in the study.
The regions with the most acceleration in thinning among girls have been linked to social cognitive functions, such as recognizing and processing faces and expressions; processing social and emotional experiences; the ability to have empathy and compassion; and language comprehension, according to the study. The regions affected in boys’ brains are involved in processing objects in the visual field as well as faces.
Based on previous research, the authors think the findings may be due to a phenomenon known as the “stress acceleration hypothesis.” This hypothesis posits that in a high-stress environment, development may shift toward maturing earlier to protect the brain’s emotional circuits and regions involved in learning and memory — reducing the harm of adversity on structural development.
There have also been reports of correlations between saliva cortisol levels and cortical thickness in the frontal lobe among human adults. Sex differences could be due to the varying effects of stressors on boys versus girls based on what’s important to each, the authors said.
What you can do
Another factor the researchers don’t yet know is whether these effects on the brain are permanent, Kuhl said.
“The brain does not recover and get thicker, we know that, but one measure of whether the teens show recovery after the pandemic is over and social normalcy has completely returned, is whether their brains thin more slowly,” Kuhl added. “If that was the case, we could say that teens’ brains showed some recovery. That’s a study we can actually do in the future.”
Ensuring young people are supported in their mental health is critical, Gotlib said. Encourage in-person quality time, limit social media use and watch for behavioral changes reflecting a shift in mental health or mood so you can intervene as early as possible, Wiznitzer said.
It’s important to recognize that although the “pandemic is largely over,” its effects remain, Gotlib said.
“A total return to ‘normal’ may never occur,” Kuhl said via email. “These are all potent reminders of human fragility and of the importance of investing in the science of prevention and preparation for the next (inevitable) pandemic.”