As an independent replication sample, EA subjects and Hispanic subjects from the Genetics of Antisocial Drug Dependence (GADD) were assessed, as previously described (Kamens et al. 2013). Probands in Denver, CO, and San Diego, CA, were identified from treatment programs, involvement with the criminal justice system, or special schools who met at least one of the criteria for having a substance use disorder (other than nicotine dependence) and CD. Siblings of the proband, as well as one or both biological parents, were included in the sample as well. The GADD is also a longitudinal study in the 2nd wave of data collection; data from wave 1, collected between 2001 and 2006, and wave 2, collection of which began in 2009 and is ongoing, were utilized in the analyses. DNA was obtained with consent through either buccal cells or blood. The University of California and the University of Colorado IRBs approved all subject recruitment, assessment, and DNA collection procedures.
