Besides causing mental health problems in some teens, the stress of the COVID-19 pandemic also sped up the aging process in adolescents’ brains, a new study says.

Brain scans of teenagers who’d been through the pandemic showed physical changes not found in the brains of comparable age groups examined before the pandemic, said the study published in Biological Psychiatry: Global Open Science.

The pandemic brain scans showed reduced thickness in the cortex, which controls executive functioning, or the ability to do tasks like planning, paying attention, and reasoning. The scans also showed growth in the amygdala, which regulates fear and stress, and the hippocampus, which controls access to memories. These changes are “more typical of individuals who are older or who experienced significant adversity in childhood,” the study said.

“Brain age difference was about three years – we hadn’t expected that large an increase given that the lockdown was less than a year [long],” said Ian Gotlib, PhD, a professor of psychology at Stanford University and lead author of the study, according to The Guardian. The study started 8 years ago in the San Francisco Bay Area to assess gender differences in rates of depression. MRI brain scans were to be taken every 2 years, the study said, but that timeline was disrupted by the pandemic. Researchers ended up looking at the brain scans of 81 teenagers taken between November 2016 and November 2019, before the pandemic, and compared them to scans of 82 teenagers taken between October 2020 and March 2022, during the pandemic but after the end of the Bay Area shutdown.

Besides the physical changes in their brains, the second group reported more mental health problems, such as anxiety and depression. Gotlib said it’s not clear if the changes are permanent. It’s also unknown if the accelerated brain aging caused the problems. “We don’t know that yet – we are starting to rescan all of the participants at age 20, so we’ll have a better sense of whether these changes persist or start to diminish with time,” he said, according to The Guardian.