In conclusion, we find that neighborhood variables that moderated genetic and environmental influences on alcohol use in late adolescence do not show parallel moderating effects on alcohol use early in adolescence. Instead, we find analogous moderating effects on behavior problems in early adolescence: genetic influences assumed greater importance in urban settings and in neighborhoods containing more older adolescents. However, these effects were limited to girls. In addition, all 3 neighborhood variables showed main effects on alcohol use, but only in girls. These findings suggest that girls may be particularly sensitive to environmental influences. They also add to the growing literature illustrating the importance of identifying specific environments that modify genetic risk.
