The COVID Social Mobility & Opportunities (COSMO) study is a new national cohort study generating high-quality evidence about how the COVID-19 pandemic has affected socio-economic inequalities in life chances, both in terms of short- and long-term effects on education, wellbeing, and career outcomes. A representative sample of young people in England who were in Year 11 in the 2020-2021 academic year were invited to take part in the survey, with the aim of following them as they progress through the final stages of education and into the labour market. Even though many areas of life have largely returned to normal following the pandemic, the long-term trend of worsening mental health and wellbeing of young people is an ongoing issue. This research briefing examines this using data from wave 2 of the COSMO study, collected when participants were aged between 17 and 18. Symptoms of psychological distress--as measured by the General Health Questionnaire (GHQ-12)--are considered, as well as other aspects of wellbeing like bullying and harassment. Use of mental health support services and satisfaction with school support are also analysed. Additionally, indicators of physical health are presented, including self-reported general health, long-term illness, and incidence of long COVID. The mental health section of this briefing highlights the experiences of young people who report a gender identity other than male or female ("non-binary+"), given previous evidence of increased psychological distress for this group. This briefing also presents differences by sexual orientation (newly available in COSMO wave 2), given previous evidence suggesting mental health problems are more likely for LGBQ+ individuals. The scale of the COSMO study, combined with the increasing reported prevalence of non-binary identities and LGBQ+ sexualities, provides sufficient sample sizes to look at these groups whose experiences are often not possible to report in smaller studies.