Trends in mental health and behavioural outcomes in UK 10–15 year olds from 2009 to 2024

This is a longitudinal observational study aiming to describe recent trends in mental health and behavioural outcomes among UK adolescents 10–15 years-old and examine differences by socio-demographic characteristics. We used self-reported data from a household-based UK survey; 2009–2024to examine trends the prevalence of emotional problems, hyperactivity, and conduct problems (Strengths and Difficulties Questionnaire); health behaviours (diet, physical activity, social media use); parent–child relationships (conflict, communication); risk behaviours (alcohol, tobacco, vaping, staying out late); and antisocial behaviours (violence, vandalism, shoplifting). Overall, 16,356 participants provided 46,218 observations. Between 2009 and 2024, emotional problems more than doubled (from 11.4% to 27.1%), with acceleration after 2014 and again after 2019. Increases were greatest among girls (38.9% in 2024 vs. 15.8% in boys) and white British adolescents. Hyperactivity symptoms were stable up to 2017 (~ 16.1%) but rose to 27.4% by 2024, mainly in girls. Conduct problems declined steadily from 13.6% in 2009 to 11.4% in 2024, driven by reductions among boys. Peer problems rose (particularly among girls), and vaping increased sharply after 2020. In contrast, alcohol and tobacco use, staying out late, and conflict with parents all declined. Conclusion These findings align with previous reports indicating that emotional problems in early adolescence have risen at an epidemic scale while many externalising and risk behaviours have declined. The divergence of trends, and concentration of poor outcomes among girls and white British adolescents, points to specific mechanisms of risk and resilience. These findings, alongside current service demand, support urgent investment in prevention of the drivers of the increases in adolescent emotional problems.