Method:Patients with IBS, fulfilling Rome III criteria, and aged between 18 and 70, were recruited from the University Hospital of Vienna, from primary care physicians and the Austrian IBS patients' organisation by an information letter with an invitation to participate in this RCT. Patients were invited for an interview at the University hospital to confirm the IBS diagnosis according to the guidelines. Exclusion criteria were: pregnancy, bowel surgery, mental retardation, insufficient knowledge of German, a concomitant severe organic and/or psychiatric disease, and recently indicated treatment with anti-depressants. Anti-depressants at a stable dose for longer than three months were allowed for admission to the study. The time for patients to reach the hospital was not to be longer than one hour. Patients with lactose and fructose intolerance as diagnosed by breath tests were not excluded if they had had an adequate diet over a period of more than three weeks without any change of their IBS symptoms.

Randomisation and therapy If 12 patients fulfilled all inclusion criteria they were randomly assigned to one of the two study arms at a 1:1 ratio. Randomisation was done by using permutated blocks of four in order to provide a balanced allocation. The investigator who generated the randomisation schedule was independent of the rest of the trial (blinded). Randomisation was either to supportive talks and symptomatic (standard) medical treatment (SMT, IBS-symptom-related) according to the guidelines (15-17) or to GHT with SMT. The GHT protocol used was the Manchester protocol of gut-directed hypnotherapy ( ) and consisted of 10 weekly sessions (45 minutes) with six patients per group over a treatment period of 12 weeks. GHT was performed at the University Hospital by two experienced physicians, trained in Manchester (UK). At the first session patients were informed about effects of hypnosis and at the third session subjects were given a compact disc (created by hypnotherapists) for practicing at home on a daily basis (practicing was documented). After an induction of hypnosis by closing the eyes a combination of standard deepening procedures followed. Then suggestions for ego-strengthening, power of self-control and gut-specific relaxation were made with hands on abdomen and visualization of slow, rhythmic waves (water, sea, or river) in pleasant, relaxing situations. The final phase involved imagery to increase one's sense of control and self-efficacy over IBS symptoms. GHT patients received also SMT. For control patients the same frequency and duration (45 minutes, SMT) of doctor's visits were offered at the University Hospital provided by a physician with additional qualification in psychosomatic medicine. No kind of relaxation techniques was allowed for control patients during the study. Psychotherapies and (changes of) symptomatic medication were allowed for all patients if indicated. If anti-depressants were taken at a stable dose at baseline, no dose reduction or increase was allowed until the six-month follow-up.

All data were collected by study coordinators not involved in the treatment. Data were entered into SPSS 17.0 and analysed by an independent person with no information about patients' randomisation (blinded).