PTSD or post dramatic stress disorder is a mental health problem where one re-experiences the trauma through intrusive distressing recollections of the event, flashbacks, and nightmares.
A modern example of sever PTSD comes from the tragic story of US sniper Chris Kyle.
In the novel and movie, Chris has sever PTSD where even small things make him snap after serving 4 tours in Iraq. Hearing loud and instant noises and barking dogs made him very paranoid.
This sad story also shows how PTSD can affect family members and his wife and friends became afraid of him in some cases.
Common symptoms include emotional detachments, nightmares or panic attacks, agitation or hostility, and depression. However it is not limited to these. Furthermore soldiers who have being in stressful environments are more likely to feel this way over those who haven't being exposed to stressful situations.