A research team has reported important but preliminary new findings on the impact of the COVID-19 pandemic on brain development in American adolescents, 13-17 years of age.

For many youths in this country, the pandemic was a generation-defining event, the team noted, and a major source of adversity. In the spring of 2020, adolescents were affected by shelter-in-place orders issued by some local governments, which led to school closures, academic disruptions, social restrictions and reduced access to school-based mental health services. “Virtually all youth experienced adversity in the form of departures from their normal routines,” the team said. “Financial strain, threats to physical health, and exposure to increased family violence were alarmingly common.”

One recently published meta-analysis (a study of multiple completed studies) sought to quantify the impact. It found that the incidence of “internalizing symptoms” (depression, anxiety, sadness, loneliness, social withdrawal) appears to have doubled in youth since the onset of the pandemic.

Researchers led by 2003 BBRF Distinguished Investigator Ian H. Gotlib, Ph.D., of Stanford University, sought to learn whether neurodevelopment in young people was also affected by pandemic conditions. They proceeded from abundant past evidence that exposure to adversity in early life (violence, neglect, abuse, family dysfunction) is associated not only with poorer mental health but also with neurodevelopmental abnormalities that may reflect accelerated maturation or aging of the brain.

One example of accelerated brain aging is atypical decreases in cortical thickness. While the thickness of cortical tissue is expected to normally diminish with age, in youths with a history of early adversity the thinning is abnormally rapid. Researchers refer to a “brain-age gap” in such young people, measured as the equivalent of how much their brain tissue shows signs of accelerated aging, compared with unaffected peers.

Dr. Gotlib and colleagues analyzed data from 163 adolescents from the San Francisco Bay area, aged 13-17. All had been participating in a multi-year study assessing the impacts of early-life stress throughout puberty. The larger study was initiated well before the onset of the pandemic. For the current study, the team divided the participants into two equally sized groups. Data for one group, “pre-COVID,” had been collected before the pandemic. Data for the other group, which was closely matched to the first group in terms of age, sex, puberty status, early-life stress, and demographics, were obtained in the period following the lifting of the Bay Area shutdown (which lasted from October 2020 to March 2022). This group was labeled the “peri-COVID” group, since the pandemic did not end with the end of the shutdown, although the most pronounced social and physical restrictions did.

Calculations of relative “brain age” were made on the basis of measurements of: subcortical grey-matter volume; the lateral ventricles; cortical thickness; cortical surface area; and total intracranial volume. A brain-age gap estimate was calculated by subtracting adolescents’ chronological age from their predicted brain age based on the obtained measurements.

“We found that adolescents assessed during the pandemic [the peri-COVID group] have neuroanatomical features that are more typical of individuals who are older or who experienced significant adversity in childhood,” the team reported in the journal Biological Psychiatry Global Open Science. Compared with carefully matched peers assessed prior to the pandemic, those assessed during the pandemic “showed signs of advanced cortical thinning,” the team noted, as well as enlargement, by volume, of the hippocampi and amygdalae, matched pairs of brain structures on either side of the brain implicated in emotional processing and memory. There were also signs of accelerated brain maturation, the team said; adolescents who were assessed during the pandemic had “older-appearing brains.”

The impacts these findings may have for behavior—and whether they are causally related to observed behavioral problems experienced by youth during the pandemic—are not yet known and beyond the scope of the study. What did seem to be clear, the team reported, was that “the pandemic appears to have altered adolescent mental health and neurodevelopment, at least in the short-term.” Whether accelerations in brain aging make a permanent or long-lasting mark on individuals or have effects that are moderated over time is a subject for future research. Dr. Gotlib and his team will be assessing participants of the current study at age 20 to examine the persistence of pandemic-related alterations.

The team noted that their sample was of relatively high socioeconomic status. They suggested that future studies recruit a sample more representative of the broad population, particularly in light of the fact that “psychosocial and health consequences of the pandemic have been observed to be more severe among individuals from socially marginalized groups and those of lower socioeconomic status.”

The team also noted an implication important for brain researchers. If their findings are replicated, longitudinal studies like theirs that were interrupted by the pandemic cannot assume that youth who were assessed at the start of the study, prior to the pandemic, are equivalent in functioning and neurodevelopment to comparable youth assessed after the pandemic. This is a problem for science that could lead to a search for a mathematical corrective factor that might be applied in cases where pre- and post-pandemic youths are being compared.