Posttraumatic Stress Disorder 507
Cognitive moDel of ptsDThe cognitive model presented in this chapter is based on the important advances made
in the development of a cognitive perspective on PTSD by Ehlers and Clark (2000),
Brewin, Dalgleish, and Joseph (1996), and Foa and colleagues (Foa & Rothbaum, 1998;
Hembree & Foa, 2004). Key dysfunctional cognitive processes and structures have been
identified that are responsible for the persistence of the posttraumatic symptoms even
in the absence of current threat. Although these cognitive models offer a full account of
PTSD in their own right, each has proposed certain critical constructs that have played
an important role in the development of our perspective on the disorder.
Ehlers and Clark (2000) contend that two cognitive processes are critical for pro-
ducing a sense of a serious current threat in PTSD: (1) excessively negative appraisals of
the traumatic event and its sequelae, and (2) poor elaboration and contextual integra-
tion of autobiographical memory of the trauma. Negative appraisals and beliefs about
the traumatic event and its consequences, a faulty threat interpretation of one’s acute
stress reaction, a fragmented trauma memory that is biased toward retrieving informa-
tion congruent with the individual’s negative appraisals, and reliance on dysfunctional
coping strategies together contribute to the perception of current threat and the symp-
toms of PTSD (see also D. M. Clark & Ehlers, 2004). From Brewin’s dual representation
model we find that the negative appraisals of trauma are a complex product of con-
sciously perceived aspects of the trauma stored as verbally accessible memories ( VA M)
and intrusive flashbacks that reflect activation of automatic, involuntary, and sensory-
rich situationally accessible memories (SAM) of the trauma (Brewin et al., 1996; Brewin
& Holmes, 2003). The mental representation of trauma in working memory, then,
involves both conceptually based and sensory-rich information encoding that together
are responsible for the generation of PTSD symptoms (see also Dalgleish, 2004). Finally
Foa and Rothbaum (1998) argue that trauma memory in PTSD is a pathological but
highly accessible memory structure involving erroneous stimulus, response, and mean-
ing associations as well as faulty evaluation of danger. Two important stimulus elements
of the fear structure associated with the meaning of “danger” are perceptions that the
world is an extremely dangerous place and views of oneself as extremely incompetent
(Hembree & Foa, 2004). Activation of the trauma memory gives rise to the symptoms
of PTSD that are interpreted as aversive and possibly dangerous. As a consequence the
individual tries to avoid any cues that might activate the trauma memory. Although each
of these cognitive theories offers a distinct perspective on PTSD, they share a common
underlying assumption that PTSD symptoms are a result of faulty beliefs and apprais-
als of trauma- related threat as well as dysfunctional encoding and retrieval of trauma
memor y.
Figure 12.1 and the following sections present a proposed model of persistent PTSD
that organizes the cognitive basis of the disorder around three interrelated levels of con-
ceptualization.
Etiological Level
Since only a minority of individuals exposed to trauma will develop PTSD, all theories
of the disorder recognize there must be preexisting individual differences that increase
vulnerability to PTSD. In addition to certain background and psychiatric pretrauma