Genetic moderation of intervention effects can also be conditioned by other aspects of the environment. Predicting an alcohol measure similar to the one investigated here, Cleveland et al. (2015) found that interventions reduced alcohol use among adolescents who reported moderate to high levels of maternal involvement and who carried the DRD4 7+ allele. This cGxI finding was not limited to DRD4, as 5-HTTLPR variation was also related to alcohol use in the same conditional fashion, that is among intervention youth with moderate to high levels on maternal involvement. It is worth noting that in the above study, which used the same 9th grade alcohol use outcome considered in the current analyses, there was no main effect of intervention on alcohol use.
