As depicted in Figure 2, children with the A/A genotype demonstrated reductions growth rates for teacher-rated externalizing behavior in both the individual (d = .46) and group (d = .27) formats. In contrast, intervention format influenced children carrying the G allele. In the group format, carriers of the G allele showed a modest reduction in externalizing problems from pre- to post-intervention, and then appear to demonstrate an increase in teacher-rated externalizing behavior during the one-year follow-up. Carriers of the G allele receiving the individual format of the intervention demonstrated significant reductions in externalizing behavior over the course of the intervention, and showed continued reductions in externalizing behavior from post-intervention to the one-year follow-up (d = 1.16 for the difference between groups).
