PTSD is a continuously problematic reaction to a traumatic event that occurs in 9%-20% of the population who has experienced a trauma. Individuals who have PTSD are frequently unaware that their symptoms and behavior are the result of the trauma(s).

Because estimates predict that 60-90% of the population has been exposed to a traumatic event, it is important to note that not everyone who has experienced trauma will develop PTSD. Additionally, the symptoms themselves do not necessarily mean that a trauma has occurred.

The criteria are as follows:

1. 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 involved 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.
2. The traumatic event is persistently re-experienced in one (or more) of the following ways:
   1. recurrent and intrusive distressing recollections of the event, including images, thoughts, or perceptions.
   2. recurrent distressing dreams of the event.
   3. acting or feeling as if the traumatic event were recurring (includes a sense of reliving the experience, illusions, hallucinations, and associative flashback episodes, including those that occur on awakening or when intoxicated).
   4. intense psychological distress at exposure to internal or external cues that symbolize or resemble an aspect of the traumatic event
   5. physiological reactivity on exposure to internal or external cues that symbolize or resemble an aspect of the traumatic event
3. Persistent avoidance of stimuli associated with the trauma and numbing 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 arouse recollections of the trauma
   3. inability to recall an important aspect of the trauma
   4. markedly diminished 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)  
4. 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 concentrating
   4. hyper vigilance
   5. exaggerated startle response
5. Duration of the disturbance (symptoms in Criteria B, C, and D) is more than 1 month.
6. The disturbance causes clinically significant distress or impairment in social, occupational, or other important areas of functioning.