Although no main effects directly relating to PTSD were found associated with the FKBP5 polymorphism, some data suggest that the regulation of the amygdala related to the hypothalamic-pituitary-adrenal (HPA) axis stress-related genes can be altered after exposure to trauma during a critical period, and these early developmental alterations may then increase the risk of developing PTSD [49]. Here, FKBP5 is linked to post-traumatic stress disorder.