OXTR and major depressive disorder: Although epigenome-wide association studies (i.e., EWAS) are now preferred, many studies investigating the associations between maltreatment experiences, DNAm levels and depressive symptoms employed a candidate gene approach, whereby genes are pre-selected on the basis of prior knowledge regarding their neurobiological functions in terms of sensitivity to stress and/or the pathogenesis of depression, such as genes involved in neuroendocrine (FKBP5, NR3C1, OXTR), neurotransmitters (COMT, MAOA, SLC6A3, SLC6A4) and inflammatory pathways (IL6, IL10).