I've discovered a wonderful resource for people looking for more information on how hypnosis and hypnotherapy can be used to treat IBS. Its from Olafur S. Palsson, Psy.D. and he's done a great job!
It highlights twenty studies done on irritable bowel syndrome treated with hypnosis which can be found over here: http://www.ibshypnosis.com/IBSresearch.html
Troy Robins - Certified Clinical Hypnotherapist based in Oxford & Witney, Oxfordshire in the UK.