Post-traumatic stress disorder (PTSD) is an anxiety disorder that results from intense horror, fear, or helplessness in response to very traumatic events, such as military combat, violent personal assaults, severe vehicle accidents, natural disasters, bearing witness to the assault or serious injury of another person, or hearing about serious harm or death of a close relative or friend (American Psychiatric Association [APA], 1994). PTSD is often an acute stress disorder that resolves within three months to two years, but for some people it is a chronic and debilitating disorder that can persist for many years (APA, 1994; Yehuda and McFarlane, 1995; Warshaw et al, 1993).
The primary symptoms of PTSD are persistent intrusive recollections of a traumatic event, hyperarousal, avoidance of stimuli and imagery associated with the trauma, and numbing of emotional experience and withdrawal (APA, 1994).
Traumatic intrusions are the primary manifestation of PTSD. They are recurrent traumatic nightmares, recollections, or flashbacks that inadvertently enter awareness and provoke emotional and somatic disturbance. The imagery of traumatic intrusions varies in its intensity, clarity, and controllability (Brett and Ostroff, 1985). Nightmares are frequent, uncontrollable, and disorganised traumatic imagery. Conscious recollections vary from vauge feelings of discomfort to clear recollections and flashbacks. Although they are infrequent, flashbacks can be intense dissociative episodes that comprise sensory, cognitive and behavioural responses to vivid imagery of a trauma (APA, 1994).
External or internal stimuli that resemble or symbolise the trauma provoke distress, emotional lability and irritability, hypervigilance, heightened startle responses and distractibility, and heightened physiological responses (APA, 1994). As discussed below, PTSD involves a sensitivity or information processing bias for threatening information and a concomitant sensitivity of physiological responses to that information, including increased heart rate and skin conductivity.
The drive to extract meaning from a traumatic experience via intrusions has the adverse affect of creating psychological discomfort and avoidance of that discomfort (Horowitz, 1976). Despite the search for meaning, PTSD sufferers attempt to avoid the distressing thoughts or feelings about the trauma, conversation about the trauma, and any activities, situations, or people who remind them of a traumatic event (APA, 1994). These avoidance patterns are associated with emotional numbing and withdrawal, including loss of interest in previously enjoyable activities and loss of empathy and intimacy with others (APA, 1994).
Although susceptibility to PTSD is associated with prior psychiatric disorder or prior exposure to trauma or other stressful life events, a family history of psychiatric disorder, personality attributes, and social support, the primary determinant of the onset and severity of PTSD is the proximity, intensity, and duration of a traumatic event (APA, 1994; Goenjian et al, 1994; Koopman, Classen, and Spiegel, 1994; McCarroll, Ursano, and Fullerton, 1993, 1995; McNally and Shin, 1995; Schnurr, Friedman, and Rosenberg, 1993; Weine et al, 1995; Yehuda et al, 1995; Yehuda and McFarlane, 1995). To properly understand susceptibility to PTSD, we need to understand the impact of a traumatic incident upon an individual and how individuals who develop PTSD respond differently to individuals who do not develop PTSD. Given that the intensity, proximity, and duration of the trauma are the most important determinants of the development of PTSD, an appropriate understanding of susceptibility to PTSD should include an understanding of the impact of trauma on the cognitions and concomitant cognitive neurobiology of a trauma victim.
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