The study reveals that the Covid-19 pandemic might be accelerating the brain maturation process in adolescents.
Recently, a new investigation suggests that certain occurrences are causing some teenagers' brains to develop faster than usual - 4.2 years faster in females and 1.4 years faster in males, on average, according to the report published on Monday in the Proceedings of the National Academy of Sciences.
By being the first to examine variations in aging by sex, this research contributes to the current body of knowledge derived from two prior studies on the Covid-19 pandemic and accelerated brain aging among adolescents.
“This discovery serves as a significant warning about the vulnerability of the adolescent brain,” commented senior study author Dr. Patricia K. Kuhl, the Bezos Family Foundation Endowed Chair in Early Childhood Learning and co-director of the Institute for Learning and Brain Sciences at the University of Washington in Seattle, via email. “Teens require our support now more than ever.”
Substantial emotional and social development takes place during adolescence, accompanied by significant changes to brain structure and function. The thickness of the cerebral cortex reaches its peak during childhood and gradually decreases throughout adolescence, eventually continuing to decrease throughout adulthood, the authors explained.
Originally, the researchers intended to monitor typical adolescent brain development over time, starting with MRI scans they performed on the participants' brains in 2018. They planned to conduct another scan in 2020.
The pandemic postponed the second MRI by three to four years - when the 130 participants from Washington state were between the ages of 12 and 20. The researchers excluded adolescents with developmental or psychiatric disorders or those taking psychotropic medications.
The team utilized data from pre-pandemic MRIs to create a "normative model" of how 68 regions of the brain would likely develop during typical adolescence. By comparing post-pandemic MRI data to this normative model, they could see if it deviated from expectations. This normative model is similar to the growth charts utilized in pediatric offices to monitor height and weight in young children. It has also been used by other researchers to analyze the influence of various circumstances or conditions such as socioeconomic disadvantage, autism, depression, attention deficit hyperactivity disorder, or traumatic stress.
The research revealed faster cortical thinning in the post-pandemic brains of adolescents - occurring in 30 brain regions across both hemispheres and all lobes for girls, and in only two regions for boys. The prevalence of thinning amounted to 43% and 6% of the studied brain regions for girls and boys, respectively.
"This study is not groundbreaking, as the researchers acknowledge," 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 shapes the brain
The study has a few limitations, including the fact that senior author Kuhl contributed the study to the journal, allowing her to select, within certain restrictions, the peer-reviewers.
Since everyone was impacted by the pandemic, the researchers didn't have a control group. Instead, they had to use normative modeling to approximate what the normal controls might have been, Wiznitzer explained - "which is not as good as true controls but likely the best they can do."
The researchers also lacked data on participants' families' employment, financial or food security, as well as their exercise, sleep, or dietary habits. It's unknown whether the participants possibly contracting Covid-19 could have contributed to the findings.
"Their study is strong, but even then, it probably doesn't have a large enough sample to conclude that the sex difference in brain aging is a reliable finding," said Dr. Ian Gotlib, author of a 2022 study on the topic 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 - the 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 associated with social cognitive functions, such as recognizing and processing faces and expressions; processing social and emotional experiences; the ability to empathize and show compassion; and language comprehension, according to the study. The regions impacted in boys' brains are involved in processing objects in the visual field, as well as faces.
Based on previous research, the authors believe the findings may be due to a phenomenon known as the "stress acceleration hypothesis." This hypothesis suggests 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 adult humans. Sex differences could be due to the varying effects of stressors on males versus females based on what's important to each, the authors suggested.
What you can do
Another aspect the researchers are yet to determine is whether these effects on the brain are permanent, Kuhl stated.
"If, after the pandemic ends and social normality completely returns, teens' brains thin more slowly, we could say that teens' brains showed some recovery. That's a study we can conduct in the future," Kuhl added.
Supporting the mental well-being of our youth is essential, according to Gotlib. Promote face-to-face interaction and reduce time spent on social media. Keep an eye out for any behavioral shifts or mood changes that may signify a shift in mental health, allowing for early intervention, as suggested by Wiznitzer.
Even though the "pandemic seemingly ends," its impacts continue, Gotlib pointed out.
"A full return to 'normalcy' might never happen," Kuhl wrote via email. "These realizations serve as stark reminders of human vulnerability and the necessity to prioritize the field of prevention and readiness for the impending (inevitable) pandemic."
This research highlights the need for focus on teenagers' wellness and health, as expedited brain development due to certain occurrences might require additional support. According to the study, faster brain aging, particularly in females, could be influenced by the stress acceleration hypothesis.
