differences in SCL6A3 promoter DNA methylation levels between cases and controls ([100 AUD cases/98 controls]65; [171 AUD cases/160 controls]66). Additionally, the association of AUDs and DNA methylation in promoter regions of five other candidate genes (GRIN2B, HCRT, SLC6A4, MAOA, and POMC) were also examined, but the findings were either inconsistent or negative. Although, no significant DNA methylation alterations in promoter regions of GRIN2B (32 male AUD cases),67 MAOA (191 adoptees),68 and POMC (145 AUD cases/37 controls)69 were observed in AUD subjects, DNA methylation levels in promoter regions of these three genes were significantly correlated with AUD symptoms (eg, craving or symptom counts). Additionally, negative findings were obtained from Orexin A (68 AUD cases)70 and SLC6A4 (192 adoptees).71 We note that most of the studies quoted above (especially the positive ones) have small sample size, and more work is clearly needed.
