Cognitive therapy for post-traumatic stress disorder: development and evaluation

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Abstract

The paper describes the development of a cognitive therapy (CT) program for post-traumatic stress disorder (PTSD) that is based on a recent cognitive model (Behav. Res. Therapy 38 (2000) 319). In a consecutive case series, 20 PTSD patients treated with CT showed highly significant improvement in symptoms of PTSD, depression and anxiety. A subsequent randomized controlled trial compared CT (N=14) and a 3-month waitlist condition (WL, N=14). CT led to large reductions in PTSD symptoms, disability, depression and anxiety, whereas the waitlist group did not improve. In both studies, treatment gains were well maintained at 6-month follow-up. CT was highly acceptable, with an overall dropout rate of only 3%. The intent-to-treat effect sizes for the degree of change in PTSD symptoms from pre to post-treatment were 2.70–2.82 (self-report), and 2.07 (assessor-rated). The controlled effect sizes for CT versus WL post-treatment scores were 2.25 (self-report) and 2.18 (assessor-rated). As predicted by the cognitive model, good treatment outcome was related to greater changes in dysfunctional post-traumatic cognitions. Patient characteristics such as comorbidity, type of trauma, history of previous trauma, or time since the traumatic event did not predict treatment response, however, low educational attainment and low socioeconomic status were related to better outcome.

Introduction

Several versions of cognitive behavioural treatment (CBT) for post-traumatic stress disorder (PTSD) have been described in the literature. In a meta-analysis of controlled and uncontrolled studies, van Etten and Taylor (1998) concluded that CBT for PTSD is effective. The mean observed effect sizes for changes in PTSD symptoms from initial assessment to post-treatment were relatively large, Cohen’s d=1.27 for self-report measures of PTSD symptoms, and d=1.89 for assessor ratings.

The most effective programs appear to be those that rely on repeated exposure to the trauma memory (either in imagination or by writing a trauma narrative) and in vivo exposure to situations avoided since the event, on cognitive restructuring of the meaning of the trauma, or a combination of these methods. In a large randomized controlled trial, Resick, Nishith, Weaver, Astin, and Feuer (2002) compared two effective versions of CBT, cognitive processing therapy (Resick, & Schnicke, 1992, Resick, & Schnicke, 1993) and prolonged exposure (Foa et al., 1999; Foa & Rothbaum, 1998; Foa, Rothbaum, Riggs, & Murdock, 1991) with a minimal attention waitlist control. Both CBT programs led to large reductions in PTSD symptoms.

Non-trauma-focused behavioural interventions such as relaxation training are less effective than those that involve systematic exposure to the trauma memory or cognitive restructuring of the meaning of the trauma (Marks, Lovell, Noshirvani, Livanou, & Thrasher, 1998). Similarly, trauma-focused CBT is more effective than supportive counseling (Blanchard et al. 2003; Bryant, Moulds, Guthrie, Dang, & Nixon, 2003).

Despite these successes, there is room for improvement. The effect sizes in van Etten and Taylor (1998) meta-analysis are based on completer analyses, and thus represent overestimates of treatment efficacy. Recent studies have shown trauma-focused CBT to be effective in intent-to-treat analyses, with effect sizes ranging between 1.0 and 1.6 for pre to post-treatment changes in PTSD symptoms (Bryant et al., 2003; Resick et al., 2002).

However, the relatively large proportion of patients who do not complete treatment is a concern. The mean percentage of drop-outs for CBT in van Etten and Taylor (1998) meta-analysis was 15%, but some recent randomized controlled trials (RCTs) have reported higher drop-out rates of around 25% (Blanchard et al., 2003; Bryant et al., 2003; Resick et al., 2002). Furthermore, a subgroup of patients still meet diagnostic criteria for PTSD at the end of treatment. The proportion depends on the severity of initial symptoms, and ranges between 35% and 47% in recent intent-to-treat analyses (Bryant et al., 2003; Foa et al., 1999; Resick et al., 2002).

In the present paper, we describe the development and initial evaluation of a variant of trauma-focused CBT that is based on a recent cognitive model of PTSD (Ehlers & Clark, 2000). The model draws heavily on the writings of other theorists (Brewin, Dalgleish, & Joseph, 1996; Conway, 1997; Foa & Riggs, 1993; Foa & Rothbaum, 1998; Foa, Steketee, & Rothbaum, 1989; Horowitz, 1997; Janoff-Bulman, 1992; Joseph, Williams, & Yule, 1997; Keane, Zimering, & Caddell, 1985; Krystal, Bennett, Bremner, Southwick, & Charney, 1995; Litz & Keane, 1989; Markowitsch, 1996; Resick & Schnicke, 1993; van der Kolk & Fisler, 1995), but provides a unique synthesis. Ehlers and Clark (2000) suggested that PTSD becomes persistent when individuals process the trauma in a way that leads to a sense of serious, current threat. The sense of threat arises as a consequence of (1) excessively negative appraisals of the trauma and/or its sequelae and (2) a disturbance of the autobiographical memory for the trauma characterized by poor elaboration and contextualization, strong associative memory and strong perceptual priming, which leads to involuntary reexperiencing of aspects of the trauma. Changes in negative appraisals and trauma memory are prevented by a series of problematic behavioural and cognitive strategies. Accordingly, cognitive therapy (CT) for PTSD aims to modify excessively negative appraisals, correct the autobiographical memory disturbance, and remove the problematic behavioural and cognitive strategies.

Section snippets

Cognitive therapy for PTSD

For each patient, an individualized version of the Ehlers and Clark (2000) model is developed by identifying the relevant appraisals, memory characteristics and triggers, and behavioural and cognitive strategies that maintain his/her PTSD. These maintaining factors are addressed with the procedures described below. Thus, the relative weight given to different treatment procedures differs from patient to patient.

Goal 1: Modify excessively negative appraisals of the trauma and its sequelae.

Participants

Twenty consecutive patients (10 women, 10 men) who had been referred by their General Practitioners or Community Mental Health Teams for the treatment of PTSD were recruited for the case series. Their ages ranged between 18 and 64. All patients were Caucasian. Patients met DSM-IV diagnostic criteria for PTSD as determined by the Structured Clinical Interview for DSM-IV (SCID, First, Spitzer, Gibbon, & Williams, 1995). Characteristics of the sample are shown in Table 1. Patients suffered from

Patients

Twenty-eight patients were recruited from consecutive referrals from General Practitioners and Community Mental Health Teams. To be accepted into the trial, patients had to meet the following inclusion criteria: 18–65 years old; meeting diagnostic criteria for PTSD as determined by the SCID (First et al., 1995); the current episode of PTSD was linked to discrete traumatic events in adulthood; PTSD was the main problem; and time since the trauma was at least 6 months. Half of the patients

Predictor analysis

Data for patients treated the consecutive case series and in the RCT (immediate and post-wait treatment) were combined for a predictor analysis of treatment outcome. A further nine consecutive patients with chronic PTSD that met RCT criteria and were subsequently treated with CT by our group were added to increase sample size (N=57). The measure of treatment outcome was the residual gain score from the regression of pre-treatment composite PDS and PDS-distress scores onto composite scores at

Discussion

The RCT showed that CT for PTSD was superior to a 3-month waitlist condition on measures of PTSD symptoms, disability, and associated symptoms of anxiety and depression. As in the consecutive case series, the effect size for changes in PTSD symptoms with CT was very large. The effect size of 2.82 for pre to post-treatment changes with CT in the PDS in our intent-to-treat analysis compares favorably to the mean effect size of 1.27 for treatment completers for cognitive behavioural treatments of

Acknowledgements

We are grateful to the Wellcome Trust for funding this research. We thank Jessica Buckley, Antje Horsch, Anne Beaton and Carolyn Fordham Walker for their invaluable help with patient recruitment, assessments, and data entry. We thank Emma Dunmore, Claudia Herbert, Kevin Meares, Anne Speckens, and Carol Sherwood for their help with patient assessment and treatment.

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