We conducted a genetic analysis of treatment response in the Fast Track randomized control trial, a 10-year-long intervention to prevent externalizing psychopathology. We tested whether carrying certain alleles of the glucocorticoid receptor gene NR3C1 predisposed children to benefit more or less from the Fast Track intervention. We found that European-American children who carried one or two copies of the rs10482672 “A” allele benefitted from Fast Track intervention more than did their age- and sex-matched peers who did not carry a copy of this allele. The difference in treatment effect between these two groups was large. For “A” carriers, 18 percent of treated children manifested externalizing psychopathology at adult follow-up, as compared to 75 percent of control children. In contrast, for children who did not carry an “A” allele, Fast Track had no effect; 56 percent of treated children and 57 percent of control children manifested externalizing psychopathology at follow-up. Sensitivity analyses indicated that moderation of the Fast Track intervention effect on externalizing psychopathology at age 25 years by rs10482672 genotype was primarily due to increased effectiveness of the intervention in
