Can Genetics Predict Response to Complex Behavioral Interventions? Evidence from a Genetic Analysis of the Fast Track Randomized Control Trial Dustin Albert 1 Daniel W. Belsky 1 D. Max Crowley Shawn J. Latendresse Fazil Aliev Brien Riley Conduct Problems Prevention Research Group 2 Danielle M. Dick Kenneth A. Dodge Abstract Early interventions are a preferred method for addressing behavioral problems in high- risk children, but often have only modest effects. Identifying sources of variation in intervention effects can suggest means to improve efficiency. One potential source of such variation is the genome. We conducted a genetic analysis of the Fast Track ran- domized control trial, a 10-year-long intervention to prevent high-risk kindergarteners from developing adult externalizing problems including substance abuse and antiso- cial behavior. We tested whether variants of the glucocorticoid receptor gene NR3C1 were associated with differences in response to the Fast Track intervention. We found that in European-American children, a variant of NR3C1 identified by the single- nucleotide polymorphism rs10482672 was associated with increased risk for external- izing psychopathology in control group children and decreased risk for externalizing psychopathology in intervention group children. Variation in NR3C1 measured in this study was not associated with differential intervention response in African-American children. We discuss implications for efforts to prevent externalizing problems in high- risk children and for public policy in the genomic era. C  2015 by the Association for Public Policy Analysis and Management. INTRODUCTION Intervention during childhood to promote human capital development has the po- tential to prevent a cascade of negative outcomes, including poor health, criminal behavior, and overreliance on government services in the future (Anderson et al., 2003; Dodge, 2009; Eckenrode et al., 2010; Garner et al., 2011; Heckman et al., 2010; O’Connell, Boat, & Warner, 2009). Evidence of this has made strategies for investing in youth a policy priority in the United States and globally (America’s 1 Dustin Albert and Daniel W. Belsky contributed equally to the preparation of this manuscript. 2 The Conduct Problems Prevention Research Group includes Karen L. Bierman, Pennsylvania State University; Kenneth A. Dodge, Duke University; Mark T. Greenberg, Pennsylvania State University; John E. Lochman, University of Alabama; Robert J. McMahon, Simon Fraser University and Child & Family Research Institute; and Ellen E. Pinderhughes, Tufts University. Journal of Policy Analysis and Management, Vol. 0, No. 0, 1–22 (2015) C  2015 by the Association for Public Policy Analysis and Management Published by Wiley Periodicals, Inc. View this article online at wileyonlinelibrary.com/journal/pam DOI:10.1002/pam.21811