I actually thought "shell shock"
was PTSD...but this thread has been an eye-opener.
So, is Combat Fatigue an earlier form of PTSD? For instance:
Event > Combat Fatigue > PTSD?
I can't say for sure but a lot of depression and anxiety disorders in the non-combat world is more physiological, or chemical imbalance, than psychological
I think saying "a lot" is overstating it...to my understanding, depression caused by physiological reasons is still relatively uncommon compared to situational depression for civvies.
However, I do believe that environment and genetics can play a part in whether someone suffers depression, anxiety and the whatnot. We all react differently to events, for instance, and it is also interesting to note there is increasing evidence of the genetic link for mental illnesses and mood disorders.