The hippocampus becomes smaller with PTSD (post traumatic stress disorder), and this seems to be secondary to the stress hormones damaging the hippocampus. Also, the amygdala is hyperactive and involved with the re-experiencing of the trauma seen in PTSD (Carandang, 2014).
“Chapter 6 – Post Traumatic Stress Disorder.” Anxiety Protocol. Carandang C. 2014. Healthy Mind Research Corporation.