post traumatic stress disorder
PTSD isn't something that you can see just by looking at someone.
According to U.S. Department of Veterans Affairs, experts think PTSD occurs:
PTSD is short for Post Traumatic Stress Disorder. After someone goes through trauma or a life threatening event like combat, it may affect some veterans for the rest of their lives. During combat they feel that their life or others' lives are in danger and they may feel afraid or feel like they have no control over what is happening around them.
But not all veterans get PTSD. It all depends on how intense the trauma, if they were injured or lost someone important to them and how close they were to the event. It also depends on how much help and support they get after the event.
The Armed Forces has a saying, "They will prepare you for war," but they never prepare them to go home.