DUSP6 overexpression also increased mRNA levels for the kappa opioid G-protein coupled receptor, which has been implicated in memory and depression (Bilkei-Gorzo et al., 2012; Bodnar, 2023; Wang et al., 2023; Zhu et al., 2024), and additionally, OPRK1 promoter methylation that leads to reduced gene expression has been found to increase AD risk (Ji et al., 2015). This evidence concerns the gene OPRK1 and major depressive disorder.