Irritable Bowel Syndrome (IBS) is a chronic disorder of brain-gut interaction. Using the translational model of treatment development, the aim of this thesis was twofold: 1) to identify cognitive factors involved in maintaining IBS, and 2) to subsequently adapt and test a treatment addressing these factors. Previous research has highlighted the role of illness-specific cognitions (e.g., gastrointestinal symptom-specific anxiety, paincatastrophizing) for maintaining IBS, predominantly using self-report measures. Employing a cross-sectional design, I compared IBS patients and healthy participants on implicit reaction-time based measures of attentional control (i.e., executive attentional regulation) and identification with illness and health. IBS patients showed a deficit in attentional control and biased self-referential processing of information relating to health. The findings corroborated my theoretical premise that Mindfulness-Based Cognitive Therapy (MBCT) adapted for patients with IBS would address the identified maintenance factors. In order to determine the best time point to measure changes in implicit cognitive functions in mindfulness-based interventions, I designed a quasi-experimental proof-ofconcept study. It found that an increase in attentional control in healthy students can be measured after two weeks of the 'Finding Peace in a Frantic World' programme. Subsequently, a treatment protocol of MBCT for IBS was developed, which aimed to reduce IBS symptoms and increase quality of life. It was hypothesised that this treatment would alleviate symptoms by attenuating illness-specific cognitions, supported by improvements in attentional control, and by changing how cognitive, emotional, illness and health related information is processed. A randomised wait-list controlled clinical trial assessed the efficacy of MBCT for IBS at four time points. MBCT for IBS reduced IBS symptom severity by reducing maladaptive illness-specific cognitions paired with a shift towards self-referential processing of health related information and more accepting, non-judgemental processing of emotions and thoughts. These results suggest that MBCT for IBS is a promising treatment for IBS patients. The treatment protocol awaits further testing in bigger samples and with active control groups.