ference in 5-HTTLPR Promoter Methylation Variation in a Monozygotic Twin Sample (n = 84 pairs)Linear regression based on intrapair differences demonstrated that intrapair difference in BDI score was significantly associated with intrapair differences in DNA methylation level at 10 CpG sites, after adjusting for covariates including BMI, smoking (pack-year), physical activity and alcohol consumptio