SLC6A4 and major depressive disorder: Exposure to stress results in the modification of DNA methylation in several genes associated with depression, including the glucocorticoid receptor (NR3C1 or GR), mineralocorticoid receptor (NR3C2 or MR), corticotrophin-releasing hormone receptor 1 (CRHR1), serotonin transporter (SLC6A4 or 5-HTT), brain-derived neurotrophic factor (BDNF), and FK506-binding protein 5 (FKBP5) (Borçoi et al., 2021, Drzymalla et al., 2021, Ding and Dai, 2019).