(The following has been taken from, Shorter Oxford Textbook of Psychiatry Part, (2001), Michael Gelder, Richard Mayou, Philip Cowen, Post Traumatic Stress Disorder,  pg195)

“This term denotes an intense, prolonged, and sometimes delayed reaction to an intensely stressful event.

The essential features of a post-traumatic stress reaction are hyper-arousal, re-experiencing of aspects of the stressful events, and avoidance of reminders.  Examples of extreme stressors that may cause this disorder are natural disasters such as floods and earthquakes, man-made calamities such as major fires, serious transport accidents, or the circumstances of war, and rape or serious physical assault on the person.

The original concept of post-traumatic stress disorder was of a reaction to such an extreme stressor that any person would be affected.  Epidemiological studies have shown that not everyone exposed to the same extreme stressor develops post-traumatic stress disorder; hence personal predisposition plays a part.  In many disasters the victims suffer not only psychological distress but also physical injury, which may increase the likelihood of a post-traumatic stress disorder. 

Table 8.3  The principal symptoms of post-traumatic stress disorder:

Hyperarousal

Persistent anxiety
Irritability
Insomnia
Poor concentration

Intrusions

Difficulty in recalling stressful events at will
Intense intrusive imagery (‘flashfbacks’)
Recurrent distressing dreams

Avoidance

Avoidance of reminders of the events
Detachment
Inability to feel emotional (‘numbness’)
Diminished interest in activities”

(The above has been taken from, Shorter Oxford Textbook of Psychiatry Part, (2001), Michael Gelder, Richard Mayou, Philip Cowen, Post Traumatic Stress Disorder,  pg195)