One of the aspects of the many aspects of the success of hypnotherapy that has been in the news often is the beneficial effects hypnotherapy has for sufferers of IBS. See this New Scientist article: Heal thyself: self-hypnosis
IBS is known to be stress or anxiety related. So it is natural then, that hypnotherapy and self-hypnosis, that provides people with the skills to be calmer, more relaxed and confident in general – leads to reducing the effects of IBS.
See BBC News article: Hypnotherapy ‘can help’ irritable bowel syndrome