The essential feature of Posttraumatic Stress Disorder is the development of characteristic symptoms following exposure to an extreme traumatic stressor involving direct personal experience of an event that involves actual or threatened death or serious injury, or threat to the physical integrity of another person…

DSM-IV Criteria for 309.81 Posttraumatic 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 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. 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) physiological reactivity on exposure to internal or external cues that symbolize or resemble an aspect of the traumatic event 

C. 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) 

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 concentrating 
4) hypervigilance
5) exaggerated startle response

E. Duration of the disturbance (symptoms in Criteria B, C, and D) is more than 1 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 3 months 
Chronic: if duration of symptoms is 3 months or more 

Specify if: 

With Delayed Onset: if onset of symptoms is at least 6 months after the stressor.

Posttraumatic Disorder treatment:

Cognitive-behavioral therapy (CBT) is the most popular and commonly used psychotherapy for PTSD. CBT  focuses on how thoughts, feelings, and behaviors develop into patterns that maintain the fear and trauma. The intention of CBT is to use cognitive techniques to challenge unhelpful or distorted thoughts while using behavioral techniques to reduce the avoidance behaviors. 

Trauma-Focused Cognitive Behavioral Therapy (TF-CBT) 

One method of CBT treatment for PTSD is Exposure Therapy. The CBT therapist works with the patient to identify the cues or situations that the patient has been avoiding due to their fear and they slowly expose the patient while teaching relaxation and cognitive techniques to lessen the anxiety. The overall goal of CBT treatment for the patient is to overcome the irrational fears and develop skills for lessening the intensity of the strong emotions to a manageable level for the patient.

Eye Movement Desensitization and Reprocessing (EMDR)