Predictors of response to cognitive behaviour therapy for obsessive-compulsive disorder.

Response to psychological treatment for Obsessive-Compulsive Disorder (OCD) varies, and dropout and relapse rates remain troubling. However, while studies examining symptom reductions are favourable, outcomes are less encouraging when outcome is defined in terms of clinically significant change. Moreover, there is little understanding of what predicts treatment outcome. This study examined demographic, symptomatic and cognitive predictors of outcome in 79 participants undertaking individualised cognitive-behavioural therapy for OCD. After investigating differences between treatment completers and non-completers, we examined treatment response as defined by post-treatment symptom severity and clinically reliable change, as well as predictors of treatment response. Completers were less likely to present with co-morbidity. The treatment was highly efficacious irrespective of whether completer or intention-to-treat analysis was undertaken, with 58% of treatment completers considered "recovered" at post-treatment. Lower pre-treatment levels of OCD symptoms and greater perfectionism/intolerance of uncertainty were the best unique predictors of OCD severity outcomes at post-treatment. Changes in obsessional beliefs were associated with symptomatic change, although only perfectionism/intolerance of uncertainty was a significant unique predictor of post-treatment change. Recovery status was predicted only by pre-treatment OCD severity. In helping to identify those at risk for poorer outcomes, such research can lead to the development of more effective interventions.