FKBP5 polymorphisms are also associated with altered induction of mRNA, changes to hippocampal size [20], [22], as well as diseases associated with alterations in the hypothalamic-pituitary-adrenal (HPA) axis, such as post-traumatic stress disorder (PTSD) [23]–[27]. Here, FKBP5 is linked to post-traumatic stress disorder.