The exceptionally threatening character of traumatic events has been highlighted in the diagnostic criteria for PTSD (American Psychiatric Association, 1980; World Health Organization, 1992). Perceived threat to life during trauma showed consistent correlations with PTSD severity in a recent meta-analysis (Ozer, Best, Lipsey, & Weiss, 2003), with an average weighted correlation of .26. For perpetrators of violence, the perceived threat to their social status may be an important additional source of threat (Beck, 1999). It was therefore included as a possible predictor in the present study.
Emotional reactions during trauma are also highlighted in the diagnostic criteria for PTSD, in particular fear, helplessness, or horror (American Psychiatric Association, 1994). In Ozer et al.'s (2003) meta-analysis, the intensity of such negative emotions showed an average weighted correlation of .26 with PTSD severity. Other negative emotions that have been shown to predict PTSD include anger and shame (Andrews, Brewin, Rose, & Kirk, 2000).
Cognitive Processing and Disorganized Trauma Memories
Theories of PTSD suggest that information processing is compromised during trauma and that compromised information processing explains PTSD symptom severity over and above what is explained by high arousal and negative emotions (e.g., Brewin et al., 1996; Ehlers & Clark, 2000). The most widely investigated indicator of such compromised processing is dissociation, which was the best predictor of PTSD in Ozer et al.'s (2003) meta-analysis, with an average weighted correlation of .35.
Dissociation is a complex concept, and it is unclear how it relates to other forms of cognitive processing that have been shown to influence memory (Roediger, 1990; Wheeler, 1997, 2000). Ehlers and Clark (2000) suggested that two further cognitive processing dimensions, data-driven processing (i.e., the predominant processing of sensory as opposed to conceptual information) and lack of self-referent processing (i.e., failure to encode new information as related to the self and other autobiographical information), predict whether people develop reexperiencing symptoms after trauma. These processes are thought to overlap in part with aspects of dissociation. Preliminary empirical support for a role of data-driven processing and lack of self-referent processing in intrusive trauma memories was found in studies of trauma survivors and volunteers exposed to distressing films (Murray, Ehlers, & Mayou, 2002; Rosario, Williams, & Ehlers, 2006).
Compromised cognitive processing is thought to lead to deficits in the autobiographical memory for the traumatic event. There are different hypotheses about the nature of this deficit, including a deficit in memory representations that facilitate intentional recall (Brewin et al., 1996), highly fragmented memories (e.g., Foa & Riggs, 1993; Herman, 1992), and poorly elaborated memories that are inadequately incorporated into their context of other autobiographical memories (e.g., Ehlers & Clark, 2000). Poor elaboration is thought to lead to poor inhibition of unintentional triggering of aspects of the trauma memory by matching cues. Ehlers, Hackmann, and Michael (2004) further suggested that the poor elaboration should be most pronounced for those parts of the trauma that are later reexperienced.
The mechanisms involved with the formation of trauma memories and deficits in recall specified in the different PTSD models are difficult to measure (Ehlers et al., 2004; McNally, 2003). One way is to code narratives of the traumatic event for indicators of the hypothesized mechanism. Common to the fragmentation and poor elaboration models is the hypothesis that intentional recall of trauma memories should be disorganized. Several studies have shown preliminary support for more disorganized trauma narratives in patients with PTSD versus those without PTSD (Foa, Molnar, & Cashman, 1995; Halligan, Michael, Clark, & Ehlers, 2003; Murray et al., 2002) and in volunteers exposed to a highly unpleasant film who developed intrusive memories than those without subsequent intrusions (Halligan, Clark, & Ehlers, 2002).
Appraisals of the Trauma and Its Aftermath
PTSD has been found to be associated with excessively negative appraisals of traumatic events (Ehlers & Clark, 2000; Foa & Riggs, 1993; Resick & Schnicke, 1993). For example, trauma survivors who blame themselves for the event or those who appraise a traumatic event as a sign of a negative (e.g., incompetent, unworthy, inadequate) self have more persistent PTSD symptoms than those who do not (Andrews et al., 2000; Dunmore, Clark, & Ehlers, 1997, 1999, 2001; Ehlers, Maercker, & Boos, 2000; Foa, Tolin, Ehlers, Clark, & Orsillo, 1999).
Although it is common for people to experience temporary unwanted memories following trauma, only a subgroup suffer from persisting intrusive memories (e.g., Baum & Hall, 1993). Ehlers and Steil (1995) suggested that negative interpretations of intrusions and other PTSD symptoms contribute to the maintenance of intrusive memories because they motivate the survivor to engage in behaviors that prevent processing of the trauma and may even increase intrusion frequency (e.g., rumination, thought suppression, use of alcohol and drugs). Several studies have supported the role of negative interpretations of intrusions in maintaining intrusions and PTSD (e.g., Dunmore et al., 1999, 2001; Ehlers, Mayou, & Bryant, 1998). Other trauma sequelae may also be interpreted in a negative way, contributing to the maintenance of PTSD (Ehlers & Clark, 2000). A common example is that trauma survivors interpret the trauma and its consequences as meaning that they have permanently changed for the worse as a person. Perceived permanent change has been shown to predict chronic PTSD (Dunmore et al., 1999, 2001; Ehlers et al., 2000).
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