"Thinning of the cortex is not necessarily bad; some scientists frame the process as the brain rewiring itself as it matures..."

"... increasing its efficiency. But the process is known to accelerate in stressful conditions, and accelerated thinning is correlated with depression and anxiety. Scans taken in 2021, after shutdowns started to lift, showed that both boys and girls had experienced rapid cortical thinning during that period. But the effect was far more notable in girls, whose thinning had accelerated, on average, by 4.2 years ahead of what was expected; the thinning in boys’ brains had accelerated 1.4 years ahead of what was expected.... The difference between the genders 'is just as clear as night and day,' Dr. Kuhl said. 'In the girls, the effects were all over the brain — all the lobes, both hemispheres.'"

From "Teen Girls’ Brains Aged Rapidly During Pandemic, Study Finds/Neuroimaging found girls experienced cortical thinning far faster than boys did during the first year of Covid lockdowns" (NYT).