Our study builds on and extends the work of prior GxI studies by providing evidence of G x I interaction involving GABRA2 that changes with development and appears strongest for early-to-mid adolescent alcohol misuse. Our results suggest the possibility that the TT genotype is associated with differential susceptibility to environmental effects on alcohol misuse given that (a) control adolescents with the TT genotype showed higher levels of alcohol misuse throughout adolescence, whereas in the intervention group, TT youth showed lower levels of early to mid-adolescent alcohol misuse; and (b) the intervention reduced alcohol misuse for adolescents with the TT genotype but not for adolescents carrying the A allele, which suggests that adolescents with the TT genotype were significantly responsive to the intervention as would be expected if the TT genotype is indeed associated with differential susceptibility.
