Our analysis focused on the glucocorticoid receptor gene NR3C1, which encodes a protein critical to human stress physiology. We studied Fast Track participants who provided genetic data at age 21 and interview reports on externalizing problems at age 25. We tested genetic moderation effects separately in European-American (N=242) and African-American (N=248) subsamples. We found that a common NR3C1 variant, identified by the single nucleotide polymorphism (SNP)iv rs10482672, significantly moderated the effectiveness of the Fast Track intervention among European-American participants. The less common “A” allelev of this SNP identified children who were both (1) especially likely to develop externalizing psychopathology if they did not receive the Fast Track intervention; and (2) especially likely to benefit in terms of reduced likelihood of developing externalizing psychopathology if they did receive the Fast Track intervention (18 percent of treated “A” carriers as compared to 75 percent of control “A” carriers manifested externalizing psychopathology at age 25 years; in contrast, 56 percent of treated non-carriers and 57 percent of control non-carriers manifested externalizing psychopathology at age 25 years). Analyses examining children’s substance use and delinquent
