BDNF and major depressive disorder: Four of them had a candidate gene approach (Kleimann et al., 2015; Neyazi et al., 2018; Moschny et al., 2020b; Schurgers et al., 2022), focusing on genes that have been frequently associated with the molecular pathophysiology of MDD, such as BDNF and NR3C1. Although preliminary and without overlap regarding the assessed CpGs on DNA sequence, Kleimann et al. (2015) and Schurgers et al. (2022) presented evidence suggesting that ECT response is associated with a demethylation pattern of BDNF (e.g., exon 1 promoter).