One of the most critical factors underlying the delay in progression among very early drinkers may be limited opportunity to obtain and consume alcohol. Increased alcohol use and problems in youth are associated with greater alcohol availability, especially access through social sources such as parents, siblings, and friends [37]. Later onsetting youth are likely to show greater pubertal development at first drink (by virtue of being older) and hence may have greater access to alcohol, perhaps via older friends/romantic partners. Additionally, the opportunity to consume alcohol is limited by parental monitoring and supervision [38], which is likely to be greater among younger adolescents. Finally, older adolescents may be more likely to be exposed to alcohol content via advertising and the media, which have been shown to influence adolescent alcohol use [39,40], perhaps through peer influence and shaping of alcohol expectancies [40].
