PTSD is a psychiatric disorder that can develop after the direct, personal experiencing or witnessing of a traumatic event, often life-threatening. The essential characteristic of PTSD is a cluster of symptoms that include:

• Re-experiencing—intrusive recollections of a traumatic event, often through flashbacks or nightmares,

• Avoidance or numbing—efforts to avoid anything associated with the trauma and numbing of emotions,

• Hyperarousal—often manifested by difficulty in sleeping and concentrating and by irritability.

If those symptoms last for a month or less, they might be indicative of acute stress disorder; however, for a diagnosis of PTSD to be made, the symptoms must be present for at least a month and must cause “clinically significant distress and/or impairment in social, occupational, and/or other important areas of functioning.”

Although there is a long history of descriptions of posttraumatic syndromes, the modern era of diagnosing PTSD began in 1980 with the introduction of PTSD in the third edition of APA Diagnostic and Statistical Manual of Mental Disorders (DSM-III). Formal recognition of PTSD led to a large body of systematic research on its features and research findings led to modification and refinement of the diagnostic criteria. But many of the diagnostic criteria from DMS-III are largely unchanged in the latest revision of the fourth edition of the diagnostic manual, DSM-IV-TR (hereafter referred to as the DSM-IV).

The evidence-based diagnosis of PTSD, according to DSM-IV (see Box 2.1) has several components: exposure to a traumatic event, intrusive re-experiencing of the event, avoidance and numbing,