The American Psychiatric Association (APA) specifies the symptoms and criteria for PSTD in its Diagnostic and Statistic Manual of Mental Disorders:

Diagnostic Criteria for Post-Traumatic Stress Disorder

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. Note: In children, this may be expressed instead by disorganized or agitated behavior.
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. 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.
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. Hypervigilance
   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.

Several semistructured interviews assess the DSM IV criteria for PTSD like Structured Clinical Interview for DSM IV (SCID), And the Anxiety Disorders Interview Schedule for DSM IV (AIDS-IV).  Another tool used to evaluate symptoms of PTSD is the Clinician-Administered PTSD Scale (CAPS), a self-reporting questionnaire that assesses the nature of trauma, the patient's current condition, and the prognosis. The CAPS also helps identify associated conditions or complications, such as guilt and an impaired sense of surroundings.

Differential Diagnosis
Other conditions cause many of the symptoms experienced in PTSD and these conditions must be ruled out. Additionally, conditions such as substance abuse and depression develop as complications of PTSD. Ultimately, the distinguishing factor is the fact that the patient has experienced a severe trauma.

Some of the conditions that must be ruled out include the following:

• Acute stress disorder (duration of upto 4 weeks)
• Adjustment disorder (less severe stressor or different symptom pattern)
• Mood disorder or other anxiety disorder (symptoms of avoidance, numbing, or hyperarousal present before exposure to the stresor)
• Other disorders with intrusive thoughts or perceptual disturbances (e.g. obsessive compulsive disorder, schizophrenia, other psychotic disorder)
• Substance abuse or dependence disorder

Course
The course of PTSD is often determined on when the person begins to experience symptoms.

Immediate Onset

• Better response to treatment
• Better prognosis (i.e., less severe symptoms)
• Fewer associated symptoms or complications
• Symptoms are resolved within 6 months

• Associated symptoms and conditions develop
• Condition more likely to become chronic
• Possible repressed memories
• Worse prognosis

Working with repressed memories in therapy is controversial, because many therapists doubt their validity and accuracy. Repressed memories are typically retrieved during hypnosis, which many psychiatrists consider an unreliable tool for memory exploration.

About 50% of those who have acute onset of symptoms recover within 6 months. Roughly 30% develop chronic symptoms that may affect them for the rest of their lives. Others experience intermittent periods of symptom severity and remission.

Next: Treatment- Psychotherapy