COMT and Borderline personality disorder: Average and individual CpG-site methylation levels of each HTR2A, NR3C1, MAOA, and COMT were significantly increased in BPD subjects, MAOB by trend. Significantly higher methylation was found in most of the analyzed single CpG sites: HTR2A (4 CpG sites), NR3C1 (2 of 8 CpG sites), MAOA (1 of 5 CpG sites), MAOB (1 of 6 CpG sites) and COMT (2 of 4 CpG sites).