In the case of the FKBP5 gene, which encodes the FKBP51 protein (cis-trans prolyl isomerase), its most important function is to influence binding affinity in glucocorticoid receptor signaling [33], which is hypomethylated in people who attempted suicide and also in patients with depression and suicidal ideation [20,24]. Here, FKBP5 is linked to major depressive disorder.