During the course of a lifetime approximately half of all American men and women will be exposed to at least one traumatic event such as assault, military combat, an industrial or vehicular accident, rape, domestic violence, or a natural disaster such as an earthquake. (Rates are much higher, of course, in countries at war and in those subjected to oppressive governments or state terrorism.) Although most Americans will be able to absorb the psychological impact of such an experience and resume their normal lives, a sizable minority (approximately 8%), will suffer significant distress or impairment in social, occupational or other important areas of functioning (Kessler, Sonnega, Bromet, et al., 1995).

When such post-traumatic symptoms or impairments in everyday functioning persist for at least a month and sometimes for life, it is called Post-Traumatic Stress Disorder (PTSD). PTSD has been recognized by many other names by writers since antiquity and by modern psychiatry since the late 1800s. It was defined as a distinct psychiatric diagnosis in 1980 when the American Psychiatric Association published its revised diagnostic manual, the Diagnostic and Statistical Manual of Mental Disorders- Third Edition (DSM-III) (American Psychiatric Association, 1980). As a result, for almost 20 years clinicians have utilized PTSD as a diagnostic tool and developed corresponding treatments.

Before discussing PTSD, however, we must first turn our attention to our definition and growing understanding of trauma.