Reacción a "Pandemic related isolation accelerated the brain maturation in adolescents, especially in girls"

It is important to rigorously study the impact of the COVID-19 pandemic in adolescent health and this study is a useful contribution. It is important, however, not to over interpret the results in this paper for the following reasons:

1. They are measuring the thickness of the grey matter at the edge of the brain from MRI scans. These scans don't actually measure number of brain cells or their connections, nor link directly to any brain symptoms. So the observation that there is "accelerated cortical thinning" does not necessarily tell us about any actual long term harm to the adolescents.
2. While the overall number of brain scans is reasonable (160 pre pandemic and 130 post pandemic) these are subdivided into subsets for training the model, validating the model, and then testing the model to measure effect. Furthermore the analysis is divided between male and female subjects. As a result there are only 29 male and 25 female subjects in the test group, divided into 3 age groups (e.g. only 10 male and 8 female ages 16).  This relatively small number of subjects reduces the confidence that we can have in the conclusions.
3. The authors separated their data into training and validation in order to build their model of normal adolescent brain development. However they did not use truly independent datasets to test and validate their model.  When a validation set is not truly independent, there is a risk that the validation results will exaggerate the model performance.
4. It seems very likely that the adolescents studied had different experiences of lock down, and different post-pandemic impact on their health and lives. This study does not take account of individual isolation in lockdown nor of any subsequent psychological symptoms, so the proposed link between accelerated cortical thinning and potential harm to mental health is not derived from the data in this study, but by reference to other studies.
5. The study does not report individual subject cortical thinning based in an analysis of each subject's pre- and post- pandemic brain scans. But rather uses a model to estimate accelerated brain aging.  This does make their results sensitive to any limitations of the model.

While the authors propose that there is a need for "ongoing monitoring and support to individuals who were adolescents during the COVID-19 pandemic", their paper does not demonstrate that the sort of brain scans and modem used in this study could be of clinical use in that monitoring, so this paper does not support scanning of brains of adolescents who experienced lockdown.