The majority of people experience acute stress symptoms following trauma, but the development of posttraumatic stress disorder is the exception rather than the rule. Some investigators hypothesize that PTSD develops following increased nervous system response to trauma. Why only a minority of individuals experience this response, what their risk factors are and when should they be treated is the subject of ongoing research.
Posttraumatic stress disorder develops in response to experiencing, witnessing or even learning about a terrifying event. The event--or trauma--is usually life-threatening, or at least capable of producing bodily harm, and it typically involves either interpersonal violence or massive disaster (e.g., rape, assault, torture, terrorism, car or plane crashes, earthquake, tornado, or flood). Traumatic events have in common the ability to elicit intense and immediate fear, helplessness, horror and distress. These subjective responses lead to a cascade of adverse psychological reactions that can result in the symptoms of PTSD and the resultant disability that is associated with this condition.
The diagnosis of PTSD did not appear in the DSM until 1980. This reflected the reluctance of the mental health field to recognize that the psychological effects of traumatic experiences could be long lasting. Prior to 1980, stress-related symptoms were generally viewed as transient and not requiring intensive treatment. This was in keeping with the pervasive feeling that, with time, people ought to be able to "get over" the effects of a traumatic experience and "move on" without noticeable impairment. According to the DSM and DSM-II, people who developed long-term symptoms following trauma were perceived as constitutionally vulnerable (Yehuda and McFarlane, 1995). The diagnosis of PTSD was meant to pave the way for an improved understanding of the long-term, and possibly even permanent, impact of trauma exposure. Ultimately, systematic testing of hypotheses about the relationship between trauma exposure and long-term symptoms has led to a better understanding of the causes of PTSD and its longitudinal course and biologic basis.
Clinical Features of PTSD
Posttraumatic stress disorder defines a rather specific syndrome in which trauma survivors are unable to get the traumatic event out of their minds. Three symptom clusters are associated with PTSD: 1) reexperiencing symptoms refers to distressing images, unwanted memories, nightmares or flashbacks of the event that cause distress and attendant physical symptoms such as palpitations, shortness of breath and other panic symptoms; 2) the avoidance of reminders of the event, including people, places or things associated with the trauma and becoming emotionally numb, constricted or generally unresponsive to the environment; and 3) hyperarousal, which is reflected in physiological symptoms such as insomnia, irritability, impaired concentration, hypervigilance and increased startle responses. To meet DSM criteria for PTSD, symptoms in each of the three domains must not only be present, but also must be severe enough to cause substantial impairment in social, occupational or interpersonal domains. Furthermore, symptoms must be present for at least one month.
Posttraumatic stress disorder is the fourth most common DSM-III-R disorder, afflicting 7% to 14% of the population at some time in their lives (Yehuda, 2002). Although exposure to trauma is thought to be the major cause of PTSD, there is a marked discrepancy between the number of people exposed to trauma and the number of people who develop PTSD. If one considers the prevalence of PTSD solely among individuals who have been exposed to a potentially traumatic event as defined by the DSM-IV, it would become clear that only about 9% of men and 20% of women who are so exposed develop this disorder (Kessler et al., 1995).
The nature of the trauma experienced seems to be a highly significant factor in determining whether PTSD will develop. Events involving interpersonal violence, such as torture, rape, assaultive violence and combat, are more potent elicitors of PTSD than experiences such as motor vehicle accidents and natural disasters. The former events produce PTSD in as many as 50% to 75% of trauma survivors, whereas the latter types of events often result in PTSD