allele frequency (MAF) less than 2% were not included in analyses. 27 SNPs were removed from further analyses because deviations from Hardy–Weinberg equilibrium in ATR controls exceeded Bonferroni correction for the total number of remaining SNPs (0.05/1457 = 3.43 × 10−5). An examination for cryptic relatedness found 25 instances in which the calculated proportion of shared alleles identical by descent exceeded 0.5, indicative of greater sharing than expected for unrelated individuals; in each case, the participant with the higher project identifier number was excluded. For the final sample, the mean call rate for 136 opioid receptor SNPs that remained after data cleaning exceeded 99.9%.
