Brain shrinkage

The hippocampus shrinks by 8% following traumatic emotional stress, and this may reduce memory and learning capacity. The shrinkage was much worse, 22% to 26%, in veterans who were involved in more intense combat and had more severe post traumatic stress disorder symptoms.

Perhaps the hippocampus does not shrink; it's just that people with a smaller hippocampus are more likely to show symptoms of emotional trauma.