Predictors of symptom improvement in CBT for OCD

Cognitive behavioural therapy (CBT) is a highly effective treatment for obsessive-compulsive symptoms. However, there is contention about the mechanisms of symptom improvement in CBT for Obsessive-Compulsive Disorder (OCD). The present investigation explored the role of idiographic responsibility interpretations as a mechanism of symptom improvement in CBT for OCD. The investigation consisted of three studies. Study 1 and 2 used the Responsibility Interpretations Questionnaire (RIQ) to assess responsibility interpretations, Obsessive-Compulsive Inventory - Revised (OCI-R) to assess obsessive-compulsive symptoms, Generalised Anxiety Disorder- 7 (GAD-7) and Patient Health Questionnaire- 9 (PHQ-9) to measure generalised anxiety and depressive symptoms. Study 1 analysed if RIQ scores predicted greater variance in OCI-R than GAD-7 and PHQ-9. Study 1 also analysed whether idiographic RIQ items (70 points or above) predicted greater variance in the OCI-R than all RIQ items and non-idiographic RIQ items (60 points or below). Study 2 used a single case study design to investigate if changes in idiographic RIQ scores were more closely linked with changes in OCI-R than non-idiographic RIQ scores. Study 3 involved a qualitative analysis of High Intensity (HI) therapists’ and OCD experts’ views on the key elements of CBT for OCD. Study 1 results showed that total RIQ and idiographic RIQ did not significantly predict obsessive-compulsive symptoms (p > .05). GAD-7 was the only significant predictor (p < .05). Study 2 showed that idiographic RIQ scores were more closely linked with change in OCI-R scores than non-idiographic RIQ scores. Study 3 revealed that HI therapists and OCD experts reported idiosyncratic interpretations as a key element of formulation and intervention in CBT for OCD. The results of Study 2 and 3 provide preliminary support for the role of responsibility interpretations in symptom improvement in CBT for OCD. The non-significant results for Study 1 may be due to the measures used. Larger sample sizes, alternative idiographic thresholds and idiographic outcome measures are required to fully substantiate the role of idiographic responsibility interpretations in CBT for OCD.