Post Traumatic Stress Disorder (PTSD) describes a spectrum of behaviors observed in those who have been exposed to traumatic events involving actual or threatened death, and / or serious injury to one's self or to others.  PTSD is the most severe form of Combat Trauma, formerly referred to as "Shell Shock" or "Battle Fatigue."   

PTSD is usually manifested in physical, cognitive, and emotional symptoms, which, if untreated, may last a lifetime. The range of individual reactions to the trauma  of combat may involve intense feelings of fear, panic, helplessness, and horror.  In its mildest form, it involves reintegration issues upon returning home from deployment.    

The symptoms of PTSD fall into 3 general categories: intrusive re-experiencing of the event in flashbacks, nightmares, or anxiety;  avoidance behaviors such as withdrawal or numbed emotions, loss of interest and detachment from others, and memory gaps about the event; and hyper-arousal such as difficulty sleeping or concentrating, anger and irritability, or panic attacks. Things which may trigger these symptoms include specific smells, sights, and sounds which bring the traumatic events to mind.

It's estimated that up to 300,000 veterans of service in Afghanistan and Iraq suffer from PTSD, and that for every person who suffers from the disease, 10 other people are either emotionally or spiritually wounded by secondary trauma resulting from PTSD behaviors.