Oh - hypnosis is definitely effective along with other techniques such as biofeedback for managing symptoms. Unfortunately, they aren't cures. There is an internationally recognized functional GI disorder clinic in Manchester headed by Prof. Whorwell who did some of the ground break working with gut directed hypnotherapy and IBS. You might check it out.
The complete definition of a functional GI disorder and a variety of types are given on the IFFGD webs site. A functional GI disorder means that there is a impairment of GI function and structural abnormalities can not be detect using conventional means (x-ray, blood test, etc.). However, technology has advance and new techniques have evolved. Recently some structural and organic changes have been identified. However, these changes many not be primary causes of a disorder but secondary effects. It will be interesting to see how this mystery unfolds.
-------------------- STABLE: ♂, IBS-D 50+ years - Science of IBS