Genes with >5 SNPs that contributed to >90 % accuracy included ACE, DRD2, HTR2A, HTR2C, HTR4, IL1A, MAOA, NR3C1, and TPH2. Thus, at least 16 unique genes (ACE, CRHR1, DRD2, HSD11B1, HTR2A, HTR2C, HTR4, IL12B, IL1A, IFNG, MAOA, MAOB, NOS3, NR3C1, SLC18A2, and TPH2) appear to be major contributors to CFS prediction by greater genetic effects either through individual or multiple (>5) SNPs. Here, SLC18A2 is linked to myalgic encephalomeyelitis/chronic fatigue syndrome.