Noteworthy, it has been shown that epigenetic mechanisms such as DNA methylation, microRNAs, and histone modifications are able to influence the development of depression (Lin and Tsai, 2019) and, with specific regard to BDNF, their altered activity can in turn affect the expression and the activity of this neurotrophic factor (Hing et al., 2018). This evidence concerns the gene BDNF and major depressive disorder.