Our results differ from those of Burk et al. (2012), who found exposure effects only in older adolescents. Whereas sociocultural differences between samples (U.S. vs. Swedish youth) could explain the difference, it may also be that onset but not later consumption is mediated by peer exposure in younger adolescents. Indeed, because onset and consumption are confounded in most youth consumption measures, including the Burk study, it is not clear whether Burk and colleagues’ results were driven by consumption or by onset. Analyses comparing peer effects on initiation versus acceleration of drinking across adolescence are needed.
