Mindfulness-based exposure and response prevention for obsessive compulsive disorder: Findings from a pilot randomised controlled trial

•Only 50% of people OCD recover after exposure and response prevention (ERP).•Mindfulness-based ERP has potential to improve acceptability and outcomes.•Our pilot RCT showed MB-ERP is unlikely to improve outcomes compared to ERP alone.•On average 6.5/10 sessions were attended with little difference between therapy arms.•Findings underline the need to be cautious in offering therapies ahead of evidence. Only about half of people with obsessive compulsive disorder (OCD) show clinically significant improvement following the recommended therapy, exposure and response prevention (ERP), partly due to poor therapy acceptability. A mindfulness-based approach to ERP (MB-ERP) has the potential to improve acceptability and outcomes. This was an internal pilot randomised controlled trial (RCT) of group MB-ERP compared to group ERP. 37 participants meeting DSM-IV OCD criteria were randomly allocated to MB-ERP or ERP. Both groups improved in OCD symptom severity. However, MB-ERP did not lead to clinically important improvements in OCD symptom severity at post-intervention compared to ERP – the minimum clinically important difference was not contained in the 95% confidence intervals. There were negligible between-group differences in engagement and MB-ERP did not appear to have broader benefits compared to ERP on depression, wellbeing or OCD-related beliefs. Conversely, MB-ERP led to medium/medium-large improvements in mindfulness compared to ERP. MB-ERP is unlikely to lead to clinically meaningful improvements in OCD symptom severity compared to ERP alone. We underline the importance of adhering to treatment guidelines recommending ERP for OCD. Insufficient attention may have been given to mindfulness practice/discussion in MB-ERP and further research is recommended to explore this possibility.