This study grows out of previous analyses of an older Finnish twin sample in which we found that urban/rural residency, migration rates, and percentage of slightly older individuals significantly moderated genetic and environmental influences on alcohol use at age 18 (Dick et al., 2001; Rose et al., 2001b). Here, we extend these analyses to a younger sample of Finnish twins and test for moderating effects of these variables on alcohol use at age 14 and behavior problems at age 12. For alcohol use, we find main effects of each of the neighborhood variables on alcohol use, but only in females. We find no evidence of moderation of genetic effects on alcohol use in either males or females. For behavior problems, we find no main effects of these neighborhood variables, but we find significant moderation effects, again limited to females. Genetic effects were higher in urban settings and in neighborhoods characterized by more slightly older adolescents, whereas, common environmental influences played a larger role in rural settings.
