Pandemic-related stress has physically altered the brains of adolescents, according to a new study from Stanford University, California. The stressors have made teens' brain structures appear several years older than the brains of comparable peers before the pandemic. The study describing the findings was published December 1, 2022, in the journal Biological Psychiatry: Global Open Science. 


Covid-19 pandemic has had a worse effect on teens than adults


The Covid-19 pandemic began in 2020. That year witnessed an increase in anxiety and depression cases in adults by more than 25 per cent compared to previous years. Not only has the pandemic affected adults, but also adolescents. The new study states that the neurological and mental health effects of the pandemic on teens may have been worse, compared to adults. 


Brains of adolescents aged during the pandemic


According to the study, the brains of adolescents who were assessed after the pandemic lockdowns ended appeared several years older than those of teens who were assessed before the pandemic. However, this is not the first time such accelerated changes in "brain age" have been seen. Before the pandemic, these changes were only seen in children experiencing chronic adversity, such as neglect, family dysfunction, violence or a combination of multiple factors. 


Covid-19 pandemic has resulted in stress for young people


The Covid-19 pandemic has resulted in significant stress and disruption for young people, the study says. This has led to alterations in their mental health and neurodevelopment. 


In a statement released by Stanford University, Ian Gotlib, the first author on the paper, said scientists already knew from global research that the pandemic has adversely affected mental health in youth, but it was not known what the pandemic was doing physically to the brains of the youth. 


Brain changes that occur naturally during puberty


Gotlib noted that as people age, changes in brain structure occur naturally. The bodies of children experience increased growth in both the hippocampus and amygdala, during puberty and early teenage years. There is increased growth in other regions including areas that control access to certain memories and help to modulate emotions. This is also the period when tissues in the cortex, an area involved in executive functioning, become thinner. 


The hippocampus is a complex brain structure with a major role in learning and memory. Amygdala is associated with emotional processes, and is located in front of the hippocampus. 


How the study was conducted


The researchers analysed the MRI scans from a cohort of 163 children taken before and during the pandemic, as part of the study. Due to the Covid-19 lockdowns, the developmental process increased in adolescents, according to the study.


Are the changes in brain structure permanent?


Gotlib said it is unclear whether the changes in brain structure observed during the study are linked to changes in mental health. He added it is not clear if the changes in brain structures are permanent. 


The study poses a question whether the teens' chronological age will eventually catch up to their 'brain age'. Gotlib said if the brain remains permanently older than their chronological age, it is unclear what the outcomes will be in the future. 


He explained that for people aged 70 to 80 years, one would expect some cognitive and memory problems based on changes in the brain. But what these changes mean for a 16-year-old person is not known.


What challenges did the researchers face?


According to Gotlib, the study was originally not designed to observe the impact of Covid-19 on brain structures. His lab recruited a cohort of children and adolescents from around the San Francisco Bay Area, before the pandemic, to participate in a long-term study on depression during puberty. However, when the Covid-19 pandemic hit, Gotlib could not conduct regularly-scheduled MRI scans on those youths. The lab had a restart nine months later.


The pandemic was not a normal event


Though Gotlib and his team restarted the practice of collecting brain scans from the cohort, the study was a year behind schedule. Had the study been conducted under normal circumstances, researchers could have statistically corrected for the delay while analysing the data. However, the pandemic was not a normal event.


Gotlib said the technique only works if one assumes the brains of 16-year-olds in the present day are the same as the brains of 16-year-olds before the pandemic, with respect to cortical thickness and hippocampal and amygdala volume.


Teens had mental health problems after pandemic lockdowns


Gotlib added that after looking at the data, the researchers realised that the brains were not the same before the pandemic and during the pandemic. He explained that compared to adolescents assessed before the pandemic, adolescents assessed after the pandemic lockdowns had more severe internalising mental health problems. 


The adolescents assessed after the pandemic lockdowns also had reduced cortical thickness, more advanced brain age, and larger hippocampal and amygdala volume, compared to those assessed before the pandemic. 


Scientists must account of accelerated brain development in future studies


Since kids who experienced the pandemic have shown accelerated development in their brain, other scientists will have to account for the abnormal rate of growth in any future research involving this generation.


Gotlib said there is no control group in the pandemic because everyone has experienced it. 


What do the researchers aim to do next?


Jonas Miller, one of the co-authors on the paper, said the findings could also have serious consequences for an entire generation of adolescents later in life. He explained that adolescence is a period of rapid reorganisation in the brain, and is already linked to increased rates of mental health problems, depression, and risk-taking behaviour. Since everyone is experiencing some kind of adversity in the form of disruption to their daily routines due to the Covid-19 pandemic, the brains of kids who are 16 to 17 years of age today are not comparable to those of their counterparts just a few years ago. 


Next, Gotlib aims to conduct further studies on the same cohort of children through later adolescence and young adulthood, in order to determine if the Covid-19 pandemic has changed the trajectory of these persons' brain development over the long term. The researcher also aims to find the changes in the brain structures of the teens who were infected with SARS-CoV-2.


The authors conclude that the Covid-19 pandemic has not only led to poorer mental health and accelerated brain ageing in adolescents, but has also posed significant challenges to researchers analysing data from longitudinal studies of normative development that were interrupted by the pandemic. 


The authors note that the research offers the strongest possibility for scientists to examine the effects of a major stressor experienced on a global scale.