Hope you are fine. Interestingly, we have currently a research proposal form here about this subject for referee. it seems it is a master's thesis of one of psychology students. MBCT techniques has been used glowingly among psychologists and some of them believe that it has a positive effect on stress related diseases such as IBS, student exam stress, and etc. But a lot of psychiatrists does not believe in this method, here. They have a strong opinion that MBCT has nothing special and it is just like other relaxation techniques like Yoga and meditation. I agree with them in some levels. But in the diseases like IBS, if you can decrease the patient's stresses and learn them a coping style, they may suffer less obviously. So, you can prescribe an anti anxiety drug for them or use a relaxation technique or both.
Also, if you interested in MBCT research i can give you more information by phone.
IBS is characterized by abdominal pain in response to psychological stressors. Therefore, mindfulness training (MT) may promote patients' coping style and nonreactive awareness of emotional and sensory experience. Results of a randomized controlled trials demonstrated that MT has a substantial therapeutic effect on severity of IBS through aiming its underlying mechanisms like psychological distress, but no evidence was found for a direct effect of CBT on IBS symptoms. Thus, the therapeutic mechanisms of CBT on IBS severity continue to be ambiguous.
I believe that it is a good research question and such kind of research can answer your question.