One promising avenue for detecting differential responses to interventions comes from genotype-environment interaction based on genetic differential susceptibility (Belsky et al. 2007; Belsky and Pluess 2009). Genotype-environment interaction studies suggest that genetic susceptible individuals are especially responsive to environmental influences. Under negative environmental conditions without sufficient resources and support, genetic susceptible individuals develop more adverse outcomes than less susceptible individuals; in positive conditions with ample resources and support such as intervention, however, genetic susceptible individuals achieve better outcomes (Belsky et al. 2007; Belsky and Pluess 2009). Supportive evidence in intervention research has been accumulating, including various outcomes such as externalizing behavior, substance use, and risky sexual behavior (Bakermans-Kranenburg and van Ijzendoorn 2015; van Ijzendoorn and Bakermans-Kranenburg 2015). Interventions with RCTs provide stronger tests of genotype-environment interaction than correlational studies because randomized experiments provide more statistical power, reduce measurement error, and avoid the potential problem of genotype-environment correlation, wherein individuals’ environmental experience could be driven by genetic liability (Bakermans-Kranenburg and van Ijzendoorn 2015; van Ijzendoorn and Bakermans-Kranenburg 2015).
