Because, in most cases, a biological relationship existed between the youth and caregiver, it is possible that the observed interaction effect between youth genotype and intervention actually resulted from the effect of parent genotype youth response to treatment. Confirming the potential for such an effect, a chi-square analysis indicated a significant association between caregiver and youth genotypes (χ(1)2 = 45.25, p < .01, N = 258). The number of parent-youth dyads with similar DRD4 status was 91 for those with 4-repeat alleles only and 92 for those with at least one 7-repeat allele; the numbers, however, were significantly lower for those in the off diagonals: 36 for those in which only the parent, and 39 for those in which only the youth, had a 7-repeat allele.
