Applying a developmental perspective to these mixed findings, a relatively consistent picture emerges. Significant interactions between DRD4 and environmental influences are more often found in early childhood and in adulthood, but less so in adolescence. One study with adolescents even found the opposite pattern of interactions, with carriers of the long DRD4 allele being less sensitive to the effects of peer victimization and social well-being on delinquency (Kretschmer et al., 2013). For alcohol use specifically, behavior genetic studies show a clear developmental pattern of primarily environmental influences on alcohol use in adolescence, followed by an increasing role of genetic factors in adulthood (Dick et al., 2006; Kendler et al., 2008). These results suggest that G × E interactions, including those involving DRD4, may not emerge in adolescence when genetic influences on alcohol use are minimal. Together, studies on DRD4 by environment interactions across developmental periods and behavior genetic studies of alcohol use suggest that interactions between DRD4 and peer drinking may manifest developmentally later in adulthood, but not in adolescence.
