Previous studies have reported significant decreases in the expression of BDNF in the hippocampus in animals exhibiting PTSD-like behavior (Kozlovsky et al. 2007; Zohar et al. 2011), and a preservation of BDNF expression in animals that appeared to be more resilient to similar stressors (Cohen et al. 2012; Hoffman et al. 2015a, b). Here, BDNF is linked to post-traumatic stress disorder.