Highlights

Adolescent risk behaviours declined markedly in high-income countries, 1999–2019.•

The causes are complex and not fully understood; evidence to date is reviewed.•

Less unsupervised in-person socialising led to declines in many risk behaviours.•

Behaviour-specific factors contributed to smoking and drinking declines.•

Drinking and smoking declines may have led to declines in sex, drugs, crime.

Abstract

In many high-income countries, the proportion of adolescents who smoke, drink, or engage in other risk behaviours has declined markedly over the past 25 years. We illustrate this behavioural shift by collating and presenting previously published data (1990–2019) on smoking, alcohol use, cannabis use, early sexual initiation and juvenile crime in Australia, England, the Netherlands, New Zealand, and the USA, also providing European averages where comparable data are available. Then we explore empirical evidence for and against hypothesised causes of these declines. Specifically, we explore whether the declines across risk behaviours can be considered 1) a ‘unitary trend’ caused by common underlying drivers; 2) separate trends with behaviour-specific causes; or 3) the result of a ‘cascade’ effect, with declines in […]