OPRM1 and Fever: For menstrual fever (QOL impact), we observed a nominally significant association signal at chr6:154.33–154.46 Mb (top SNP: rs17181171; P = 1.98 × 10−8) that overlaps over half of the 5′-end of the opioid receptor mu 1 (OPRM1) gene (Fig. 5a) and contains 65 high LD SNPs (Supplementary Worksheet S6).