Posttraumatic Stress Disorder

Prevalence and Etiology of Trauma and PTSD

Epidemiological studies have found that 40% to 90% of the general population in the United States experience a traumatic event meeting the PTSD Stressor criterion at some point during their lifetime. After trauma exposure, the probability of developing PTSD is estimated to be approximately 10% in the general population, although higher rates (i.e., closer to 25%) have been observed after traumatic events involving violence or life threat such as rape and military combat. Numerous factors contribute to the probability of developing the disorder, with the nature and severity of the event being the most important factor. In addition, psychosocial factors such as a family history of psychiatric illness, childhood trauma or behavior problems, and the presence of psychiatric symptoms prior to the trauma appear to mediate the relationship between trauma exposure and the subsequent development of PTSD. Individual difference factors also play a role. After controlling for trauma exposure, the rate of PTSD in women is approximately twice as high as the rate for men. Research suggests that personality traits such as neuroticism and negative emotionality represent vulnerabilities for the development of the disorder, whereas characteristics such as hardiness function as resilience factors.

Terence M. Keane and David H. Barlow adapted Barlow's model of anxiety and panic to promote an understanding of the variables involved in the development of PTSD. This conceptual model suggests that biological and psychological vulnerabilities underlie the development of PTSD. When an individual is exposed to a traumatic life event, a true biological and psychological alarm occurs leading to both conditioning of stimuli present at the time of the event and to cognitions that incorporate anxious apprehension of a recurrence of the traumatic event. These emotionally charged stimuli then promote the development of avoidance strategies in order to effectively minimize the experience of aversive emotional reactions. The emergence of PTSD is a function of these variables as well as the strength of the social support system of the individual and his or her coping abilities in the aftermath of trauma exposure.

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