Hardy-Weinberg balance test
A total of 189 MAUD patients were recruited in this study, aged from 18 to 60 years old (mean age=34 years [SD=7]). In case-control studies, the Hardy-Weinberg equilibrium serves as a preliminary quality check and constitutes the cornerstone of population genetic data research30, 31. χ2 tests were performed to compare the distribution of observed genotypes with that was predicted under Hardy–Weinberg equilibrium. All 8 SNPs in our genotype study were under Hardy-Weinberg equilibrium (p>0.01), indicating that the 8 SNPs were stable in the two population groups, which allowed us to perform further investigations on the relationship between the phenotype variants and the particular disease (Table 1).