The effectiveness of combining Cognitive Processing Therapy with a case formulation approach in the treatment of Posttraumatic Stress Disorder – A randomised controlled trial

Author: Marja Elizabeth

Elizabeth, Marja, 2020 The effectiveness of combining Cognitive Processing Therapy with a case formulation approach in the treatment of Posttraumatic Stress Disorder – A randomised controlled trial, Flinders University, College of Education, Psychology and Social Work

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Objective: This thesis examined the combination of Cognitive Processing Therapy (CPT) with a case formulation approach (CPT+CF) to investigate its efficacy on improving client outcomes in terms of symptom reduction and increased therapy engagement (i.e. reduced dropout rates). I also tested whether several factors thought to contribute to treatment outcomes including client complexity, therapeutic alliance and degree of deviation from the CPT protocol, moderated the effect of treatment condition and PTSD and related outcomes.

Method: A randomised controlled trial design was used comparing CPT+CF with CPT alone (N = 93). CPT+CF consisted of the standard CPT protocol with the inclusion of a case formulation approach (both diagrammatic and narrative in format) which guided planned deviations should this be deemed necessary. Deviations from the protocol were recorded and coded for each session. Participants were assessed at pretreatment, posttreatment and at 6-month follow-up. PTSD and depression were assessed at every session, as were participants’ judgements of overall wellbeing and session satisfaction. In order to measure complicated client presentations, a checklist of 30 variables which prior research had indicated might negatively influence treatment outcomes was developed. PTSD and depression were the main outcomes of interest with levels of complication and therapeutic alliance tested as hypothesised moderators of change. Linear mixed modelling analyses were used to examine change in symptom scores with maximum likelihood estimation for missing data. Response to treatment and good end-state functioning was assessed by a reduction in symptom severity of PTSD and depression using reliable change indices and relevant cut-offs for the measures of interest.

Results: Both conditions evidenced significant improvements on primary (PTSD and depression) and secondary treatment outcomes (posttrauma cognitions, sleep, substance use, emotional regulation). Effect sizes for PTSD measures for the intent-to-treat sample (ITT) were large ranging between 2.50 and 3.66 across time points, and this was also seen for loss of PTSD diagnosis (which ranged between 80% and 94.7%) and good end-state (ranging between 71.9% and 85.7%). Contrary to expectations, there was no significant difference in dropout between the two groups (CPT: 19.1%; CPT+CF: 15.2%). Although there were no moderating effects of either client complexity or therapeutic alliance over time between the treatment conditions, there was a tentative suggestion that those not showing initial treatment response may have benefited if allocated to CPT+CF where deviations could be put in place, relative to receiving CPT alone. Examination of the utility of the case formulation approach suggested that although it was appreciated by participants in that group (borne out by qualitative and quantitative analyses), this did not translate to group level differences on outcomes between the two treatment conditions.

Conclusion: The findings replicate previous randomised controlled trials of CPT that demonstrate CPT is a highly effective therapy for PTSD. The findings are consistent with the small number of head-to-head comparisons between individualised case formulation approaches with standard manualised treatment, which have typically observed comparable outcomes between a formulation approach and standard protocol treatment. Further research is required to determine under which conditions deviating or augmenting standard PTSD treatments might confer additional benefits for PTSD sufferers.

Keywords: Cogntive Processing Therapy, CPT, case formulation, posttraumatic stress disorder, PTSD

Subject: Psychology thesis

Thesis type: Doctor of Philosophy
Completed: 2020
School: College of Education, Psychology and Social Work
Supervisor: Professor Reg Nixon