influences on regular use during adolescence. This was not the case for state-level smoking by youth, measured by the percentage of 9th to 12th graders reporting frequent smoking, which was found to be negatively associated with genetic influences on regular smoking. Within schools, the effect of genes on daily smoking decreased as the prevalence of smoking among popular students increased, suggesting that social pressures within schools moderate the heritability of daily smoking. These interactions were not found for smoking onset (95). One study also tested whether the response to a substance use prevention/intervention program varied based upon a set of five markers (rs16969968, rs1948, rs578776, rs588765, and rs684513) and found that there was a main effect of both the intervention (b=−0.24, p-value<0.05) and genotype at rs16969968 (b = 0.14, p-value <0.05) on high school smoking. The genotype × intervention interaction effect was also found, where those with the A/A and G/A genotypes reduced their levels of smoking to levels similar to those with G/G genotypes following the intervention phenotype (G/G vs. A/A: b = −0.67, p < 0.05; A/G vs. A/A: b = −0.61, p < 0.05; G/G vs. A/G n.s.) (97).
