A cognitive-therapy-based model of PTSD has been presented by Ehlers and Clark (2000). The main core of the theory is centred on the proposal that there is a cyclical process that maintains a current and continuing sense of threat, analogous to the cycle that leads to panic in Clark's (1986) model of panic presented earlier in the chapter. The sense of threat is based on the past traumatic event, the nature of the trauma memory, and the negative appraisal of the trauma and its consequences. The cycle of continuing sense of threat is therefore based on key appraisal processes that link the approach to appraisal theories of emotion (Scherer, 1999; Scherer et al., 2001; see Chapter 3). These appraisals can be about the nature of the event, which for example could imply that "nowhere is safe" or that "the next disaster will strike soon"; alternatively, the subsequent symptoms experienced can be appraised to mean "I'm going mad" or "I'll never get over this" (Ehlers & Clark, 2000, p. 322).
The second main component in the Ehlers and Clark (2000) model is the nature of the traumatic memory. Consistent with previous theorists, they emphasise that the traumatic memory is typically not integrated with other autobiographical memories, and have shown that many of the memories can be predominantly sensory-driven, similar to proposals within Foa's and Brewin's models considered above (Halligan, Michael, Clark, & Ehlers, 2003). Finally, the individual may resort to a variety of avoidance-based strategies that can include avoidance both of situations connected to the trauma and of emotions and emotion-provoking cognition, the net effect of which is to retard cognitive change processes.
One of the strengths of the Ehlers and Clark approach is that they have now developed an adapted form of cognitive therapy for working with individuals with PTSD (Ehlers et al., 2003). The therapy aims to change negative appraisals, to deal with the problematic unintegrated autobiographical memory, and to confront the dysfunctional coping strategies. A recent small randomised controlled trial (Ehlers, Clark, Hackmann, McManus, & Fennell, 2005) has shown stronger effect sizes than reported in a meta-analysis of previous CBT approaches to PTSD (van Etten & Taylor, 1998).
So how does Ehlers and Clark's approach fare as a theory of PTSD? As summarised by Dalgleish (2004), the approach is again based on a network level of representation and thereby lacks a representation system for a higher level of abstracted meaning. Although appraisal-based approaches to normal emotions typically involve high-level meaning systems that encode goals and plans of the individual (e.g., Oatley & Johnson-Laird, 1987), this level is not articulated within the Ehlers and Clark model, even though the threat or challenge to such high-level goals and assumptions is often central to the PTSD reaction (Janoff-Bulman, 1992). The appraisal system is also not articulated within the model but is simply presented as a given; the question is which appraisal system, based on which appraisal theory, does the model incorporate? This latter problem is of course the problem faced by all stand-alone disorder-centred theories: How do they relate to more general theories of pychological functioning? Finally, the model may fall foul of the problem raised against Clark's (1986) model of panic, in that it may not be falsifiable as a theory (Roth et al., 2005).
In summary, there are a number of good, useful models of post-traumatic stress, within both the social-cognitive and information-processing approaches. However, each model, while being able to account for some aspects of the psychology of trauma very well, seems to struggle with one or more important questions central to an understanding of PTSD and associated conditions. We have tried to argue that a multi-level theory of emotion such as DRT (Brewin et al., 1996) is able to offer greater explanatory power when applied to post-traumatic stress, and in the next section we examine in some detail how the SPAARS approach attempts to account for PTSD and related conditions.
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