to avoid false positives in the GWAS driven by population stratification (i.e., differences in allele frequencies between populations) (for a review see Cardon & Palmer, 2003). We focused on the adolescent (Adolescent subsample; ages 12-17) and young adult (Young Adult subsample; ages 18-24) participants in the family-based sample who are also part of the COGA Prospective Study of the developmental antecedents of alcohol dependence (Dick et al., 2013). The adolescent and young adult prospective participants were recruited into the Prospective Study beginning in 2004, and have been followed-up biennially ever since.
