Background Risk-taking health behaviours initiated during adolescence can track into adulthood and influence lifelong health and social outcomes. Promoting positive mental health, particularly through enhancing competencies (such as pro-social skills), may help prevent the development of risk-taking behaviours and thus support future health. We investigated the relationship between skills-based components of positive mental health in childhood (Mental Health Competence, MHC) and teenage risk-taking behaviours, using data from a UK-representative population cohort, the Millennium Cohort Study (∼18 000 children born 2000–2002).

Methods Cohort members (CMs) reported on a number of common risk-taking behaviours at 14 years(y), categorised as follows: ever tried cigarettes (yes/no), ever tried e-cigarettes (yes/no), alcohol consumption (never tried, tried binge-drinking [5+alcoholic drinks at a time], tried but never binge-drinking), ever tried illegal drugs (yes/no), ever engaged in antisocial behaviour (yes/no, any of: theft, graffiti, public property damage, carrying a weapon, using a weapon, breaking and entering), and sexual contact with another young person (yes/no). A four-class latent measure of MHC summarised learning skills and prosocial behaviours at 11 y (maternal report): High, High-Moderate, Moderate, Low. We used logistic regression to estimate odds ratios (OR) for binary outcomes and multinomial regression to estimate relative risk ratios (RRR) for categorical outcomes, adjusting for confounding by socio-demographic characteristics, maternal mental health and alcohol consumption, parenting at 3 y, and puberty reported at 11 y. Sample design and attrition were accounted for with weights and item missingness with multiple imputation.

Results 17% of CMs had ever tried smoking cigarettes and 18% had ever tried e-cigarettes. 49% of CMs had consumed alcohol, including 11% binge-drinking. Trying illegal drugs, displaying anti-social behaviours and having sexual contact were less prevalent (6%–10%). Compared to CMs with High MHC, those with Low, Moderate, or High-Moderate MHC at age 11 were more likely to have taken part in risk-taking behaviours. After adjustment for potential confounding, elevated risks remained for Low MHC in relation to binge drinking (RRR: 1.6 [95% CI 1.1 to 2.3]), having tried smoking cigarettes (OR: 2.1 [1.5–2.9]), e-cigarettes (OR: 1.4 [1.0–2.0], illegal drugs (OR: 1.9 [1.3–2.9]), and anti-social behaviour (OR: 1.8 [1.2–2.6]) but not sexual contact (OR: 1.1 [0.7–1.6]).

Conclusion MHC at the end of childhood was associated with risk-taking behaviours in mid-adolescence in a representative UK cohort. Interventions that improve MHC skills in childhood may help reduce risk-taking behaviours at this crucial stage in the lifecourse, improving wellbeing in adolescence and into adulthood.