• While mental health declined in both groups over time, those in the pandemic experienced a worsening in their mental health:- Cases of depression increased 8.5% in those going through the pandemic versus 0.3% in the pre-pandemic group. - Cases of possible/probable mental health difficulties increased 12.8% in the pandemic group versus 4.5% in the pre-pandemic group. • Girls and those who were initially at low risk of mental health difficulties experienced greater deteriorations during the pandemic. 'With the increased focus on young people’s mental health, it is vitally important that we work to understand both what places young people at risk and what protects them under challenging circumstances. The paper ‘Changes in Secondary School Students’ Mental Health During the COVID-19 Pandemic’ is published in the journal JAMA Network Open.