Perceptual and conceptual processing as predictors of treatment outcome in PTSD

Cognitive behavioural treatment (CBT) is highly effective in treating post-traumatic stress disorder (PTSD). However, the mechanisms of change are still poorly understood. The aim of the present study was to investigate trauma processing during and after CBT for PTSD. Treatment consisted of imaginal exposure combined with rescripting. The rationale of this treatment is that dysfunctional interpretations may best be corrected by inducing new perspectives on what happened during trauma by experiencing new views and new emotions. In twenty-five chronic patients with PTSD, we tested whether an initial increase of perceptual processing and a subsequent increase of conceptual processing predicted treatment outcome. Possible changes in perceptual/conceptual processing during and after treatment were inferred from changes in trauma memories from pre- to post-treatment and from post- to 1-month follow-up. These memory parameters were assessed by analysing trauma narratives that were produced before the first treatment session, after the last treatment session and at follow-up. Consistent with predictions, a relative increase of conceptual processing after treatment predicted treatment outcome levels for both PTSD symptoms and general psychopathology at 1-month follow-up. Although a relative increase of perceptual processing during treatment also predicted treatment outcome, this effect was explained by the beneficial effect of a subsequent increase of conceptual processing. But an increase of perceptual processing during treatment was strongly related to an increase of conceptual processing after treatment. The results suggest that imaginal reliving during CBT is not crucial for symptom reduction, but it may promote conceptual processing, which in itself predicts a better treatment outcome.