We hypothesized that alleles of the glucocorticoid receptor gene NR3C1 would moderate Fast Track treatment effects because of the central role the gene plays in stress physiology. Human studies have not identified common NR3C1 variants that reliably associate with individual differences in stress physiology. We therefore took a hypothesis-free approach to analyzing variation within NR3C1, consistent with current best practice in genetic epidemiology (Dick, Latendresse, & Riley, 2011). There are many common DNA sequence variants within the NR3C1 gene. Clusters of these variants are in “linkage” (inherited together and therefore non-independent). We used a reference database (HapMaP version 3; http://hapmap.ncbi.nlm.nih.gov/) to identify variants that “tagged” independent clusters of variants (Dick et al., 2009). The ten single-nucleotide polymorphisms (SNPs) identified through this tagging procedure were at least partially independent in the current samples (maximum linkage disequilibriumviii as measured by R2 equal to 0.56 (European-American) and 0.53 (African-American); Appendix Figure A1)ix.
