Adolescence is a developmental stage characterised by behavioural changes, such as increases in experimental and risk-taking behaviours. Explanations for these changes include psychological, neurobiological, and social contextual factors. To some extent, experimental and risk-taking behaviours are an expected part of growing up and tend to subside in early adulthood. Nevertheless, behavioural patterns established in adolescence can be a cause for concern as they can have adverse consequences for future prospects of individuals’ health and wellbeing, and their social and economic outcomes.

The Millennium Cohort Study (MCS) collected data from nearly 10,000 individuals across the UK on a range of risky behaviours when participants were 17 years old in 2018-2019. The behaviours examined in this report include the use of substances (alcohol, smoking, vaping, Substance use and antisocial behaviour in adolescence. Evidence from the Millennium Cohort Study at age 17 drugs), and antisocial behaviours (graffiti, vandalism, shoplifting, assault, weapon use). For some of these behaviours, data was also collected previously at ages 11 and 14. This enables the tracking of risky behaviours during the adolescent period.

This report shows overall prevalences of engagement in risky behaviours, alongside breakdowns by sex, by parental educational level, and by UK country. In terms of sample characteristics, 50% were females, 36% had parents with a university degree or above, 13% were of ethnic minority origin, and the UK nations were represented by England (84%), Wales (5%), Scotland (8%) and Northern Ireland (3%). Analyses are adjusted for survey design and attrition, so figures are nationally representative estimates of risky behaviours among young people born in the UK around the turn of the millennium.