DSM IV in 1994 published the following guidelines for a diagnosis of Post Traumatic Stress Disorder:
Diagnostic Criteria for Post Traumatic Stress Disorder

A. The person has been exposed to a traumatic event in which both of the following were present:
(1) the person experienced, witnessed, or was confronted with an event or events that involve actual or threatened death or serious injury, or a threat to the physical integrity of self or others
(2) the person’s response involved intense fear, helplessness, or horror.
Note: In children, this may be expressed instead by disorganized or agitated behavior

B. The traumatic event is persistently reexperienced in one (or more) of the following ways:
(1) recurrent and intrusive distressing recollections of the event, including images, thoughts, or perceptions. Note: In young children, repetitive play may occur in which themes or aspects of the trauma are expressed.
(2) Recurrent distressing dreams of the event. Note: In children, there may be frightening dreams without recognizable content
(3) Acting or feeling as if the traumatic event were recurring (includes a sense of reliving the experience, illusions, hallucinations, and dissociative flashback episodes, including those that occur on awakening or when intoxicated). Note: In young children, trauma-specific reenactment may occur.
(4) Intense psychological distress at exposure to internal or external cues that symbolize or resemble an aspect of the traumatic event.
(5) Physiologic reactivity on exposure to internal or external cues that symbolize or resemble an aspect of the traumatic event.

C. Persistent avoiding of stimuli associated with the trauma and numbimg of general responsiveness (not present before the trauma), as indicated by three (or more) of the following:
(1) efforts to avoid thoughts, feelings, or conversations associated with the trauma
(2) efforts to avoid activities, places, or people that arouses recollections of the trauma
(3) inability to recall an important aspects of the trauma
(4) markedly dimished interest or participation in significant activities
(5) feeling of detachment or estrangement from others
(6) restricted range of affect (e.g. unable to have loving feelings)
(7) sense of a foreshortened future (e.g. does not expect to have a career, marriage, children, or a normal life span)

D. Persistent symptoms of increased arousal (not present before the trauma), as indicated by two (or more) of the following:
(1)difficulty falling or staying asleep
(2) irritability or outbursts of anger
(3) difficulty concertrating
(4) hypervigilance
(5) exaggerated startle response

E. Duration of the disturbance (symptoms in criteria B, C and D) is more than one month.

F. The disturbance causes clinically significant distress or impairment in social, occupational, or other important areas of functioning.
Specify if:
Acute: if duration of symptoms is less than three months
Chronic: if duration of symptoms is three months of more
Specify if:
With delayed onset: if onset of symptoms is at least six months after the stressor.”