https://www.sciencedaily.com/releases/2022/11/221123114210.htm

Academics from the Universities of Cambridge and Manchester analysed the well-being and self-esteem of more than 11,000 young people from across the UK, using data collected when they were 11, and again when they were 14. The adolescents' overall 'subjective well-being' -- their satisfaction with different aspects of life (such as friends, school and family) -- dropped significantly during the intervening years.

It is widely accepted that young people's well-being and mental health are influenced by factors such as economic circumstances and family life. The research shows that notwithstanding this, well-being tends to fall steeply and across the board during early adolescence.