SLC6A4 and myalgic encephalomeyelitis/chronic fatigue syndrome: The SLC6A4 site (cg20592995) was among the top sites showing <5% difference based on magnitude difference, and showed a 3% methylation difference (nominal p = 0.038) on the 450 K array between ME/CFS GC-Hypersensitive and ME/CFS GC-Typical.