Peer Effects in UK Adolescent Substance Use : Never Mind the Classmates?

This paper estimates peer influences on the alcohol, tobacco and cannabis use of a school based sample of UK 15 year olds. We present evidence of large, positive and statistically significant peer effects in all three behaviours when classmates are taken as the reference group. When friends are taken as the reference group, using self-reports of perceived friends’ substance use, we also find large, positive and statistically significant associations with own substance use. When both reference groups are considered simultaneously, the influence of classmates on own behaviour either disappears or is much reduced in magnitude, whereas the association between own and friends’ behaviours doesn’t change. The suggestion is that classmate behaviour is primarily relevant only inasmuch as it proxies for friends’ behaviour, with classmates that are not also friends having relatively little influence on adolescent substance use