JC,
It has nothing to do with age or a specific type of event except it needs to be emotionally traumatizing. The name describes what is happening:
PTSD - Post Traumatic Stress Disorder
A Disorder that is Post, or follows, an extremely emotionally and/or physically damaging, Traumatic, situation that creates an emotional response similar to fight or flight, Stress.
Our civil servants (law enforcement, EMS, fire) suffer from this just as much as our armed services do. It also can affect anybody involved in or witnessing a traumatic event, such as a deadly fire, car accident, or assault. Our brain releases chemicals in these situations that imprint a response in our memories, and if they are not properly, or until they are properly, dealt with they will cause an on going grief reaction that can range from manic, to reclusive, to depressed, chronically ill, or violent, among many possibilities.
This is something that many "experts" (ex = has been, spurt = drip under pressure) like Di Fi do not know or understand when they start spewing their anti-veteran hate. For them to focus on one group deprives them of their Rights, and it deprives millions of others from the help they also need.