Background: 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. Methods: 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. Results: 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. Conclusions: 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.

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Little is known about the role of mindfulness and self-compassion in obsessive-compulsive disorder. This cross-sectional study examined associations of mindfulness and self-compassion with obsessive-compulsive disorder symptoms and with the obsessive beliefs and low distress tolerance thought to maintain them. Samples of treatment-seeking adults (N = 1871) and non-treatment-seeking adults (N = 540) completed mindfulness, self-compassion, obsessive-compulsive disorder, anxiety, depression, obsessive beliefs and distress tolerance questionnaires. Participants with clinically significant obsessivecompulsive disorder symptoms reported lower trait mindfulness and self-compassion compared to participants with clinically significant anxiety/depression and to non-clinical controls. Among the clinical sample, there were medium-large associations between mindfulness and self-compassion and obsessive-compulsive disorder symptoms, obsessive beliefs and distress tolerance. Mindfulness and self-compassion were unique predictors of obsessive-compulsive disorder symptoms, controlling for depression severity. Once effects of obsessive beliefs and distress tolerance were controlled, a small effect remained for mindfulness (facets) on obsessing symptoms and for self-compassion on washing and checking symptoms. Directions for future research and clinical implications are considered in conclusion. Keywords Obsessive-compulsive disorder • Mindfulness • Self-compassion • Obsessive beliefs • Distress tolerance Obsessive-compulsive disorder (OCD) is a debilitating mental health condition characterised by obsessions, i.e. persistent unwanted intrusive thoughts, images or urges that can cause significant distress, and compulsions, i.e. repetitive, ritualistic behaviours aimed at alleviating distress and/ or preventing negative outcomes (APA 2013). Obsessivecompulsive disorder is a heterogeneous disorder as obsessions can centre on contamination, harm, symmetry or taboo thoughts and compulsions include physical behaviours like Electronic supplementary material The online version of this article (

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Cognitive behavioural therapy (CBT) which includes Exposure and Response (ERP) is a highly effective, gold standard treatment for Obsessive-Compulsive Disorder (OCD). Nonetheless, not all patients with OCD significantly benefit from CBT. This has generated interest in the potential benefits of Mindfulness-Based Interventions (MBIs), either integrated with CBT, to enhance engagement with ERP tasks, or delivered as a stand-alone, first-line or therapy to augment CBT. This paper reports on two qualitative studies that involved a thematic analysis of interview data with participants in a 10-week Mindfulness-Based ERP (MB-ERP) course (study 1) and a 9-week Mindfulness-Based Cognitive Therapy course adapted for OCD (MBCT-OCD) (study 2). Whilst MB-ERP integrated a mindfulness component into a standard ERP protocol, MBCT-OCD adapted the psychoeducational components of the standard MBCT for depression protocol to suit OCD, but without explicit ERP tasks. Three common main themes emerged across MB-ERP and MBCT-OCD: 'satisfaction with course features', 'acceptability of key therapeutic tasks 'and 'using mindfulness to respond differently to OCD'. Sub-themes identified under the first two main themes were mostly unique to MB-ERP or MBCT-OCD, with the exception of '(struggles with) developing a mindfulness practice routine' whilst most of the sub-themes under the last main theme were shared across MB-ERP and MBCT-OCD participants. Findings suggested that participants generally perceived both MBIs as acceptable and potentially beneficial treatments for OCD, in line with theorised mechanisms of change.