Genotype frequencies for FAAH C385A were consistent with previous reports (see Table 1; expected frequencies are from dbSNP for rs324420). Two subjects could not be genotyped. For each intermediate phenotype tested, A/A individuals were combined with heterozygotes, and this group was compared with C/C individuals. We chose to combine groups in this manner because past reports (Sipe et al. 2002; Flanagan et al. 2006) have suggested that one copy of the A allele is associated with increased risk for substance dependence. Prior to the main analyses, tests were conducted to ensure that genotype groups did not differ on baseline variables (see Table 2).
