DRD4 and alcohol drinking: CpGs in gamma-aminobutyric acid receptor subunit beta-3 (GABRB3), pro-opiomelanocortin (POMC), neural cell adhesion molecule 1 (NCAM1), dopamine receptor D4 (DRD4), methyl-CpG-binding domain protein 3 (MBD3), 5-hydroxytryptamine receptor 3A (HTR3A) and 2B (HTR2B), and glutamate (NMDA) receptor subunit zeta-1 (GRIN1) were found to be differentially methylated in alcohol dependent patients compared to control subjects, but only the result for one CpG site in the promoter region of HTR3A withstood correction for multiple testing.