Irritable bowel syndrome (IBS) is a condition which affects the large intestine, with symptoms that include varying degrees of abdominal pain, bloating, constipation and diarrhea. Medications and lifestyle changes are generally prescribed for IBS, but medical treatments for the full range of symptoms are inadequate. Cognitive behavior therapy (CBT), a psychological treatment where therapists teach patients how to use behavioral skills to manage IBS and relieve unresolved symptoms, has been associated with improvements in symptom severity and quality of life in other clinical trials. However, CBT has certain economic and feasibility limitations that prevent the therapy from being incorporated into routine clinical settings.

The Irritable Bowel Syndrome Outcome Study (IBSOS) sought to address the limitations of standard therapist-administered CBT by developing an effective self-administered version of the treatment method. IBSOS participants were randomized into one of three treatment groups and underwent four weeks of symptom monitoring. One group received the standard ten sessions of clinic-based CBT, one group received four sessions of minimal-contact CBT, and the remaining group received four sessions of supportive counseling and education without any prescribed behavior changes. Following the symptom monitoring phase, patients underwent treatment and follow-up phases. Assessments were regularly conducted during the study and the results were evaluated between the groups.

The main objective of the Irritable Bowel Syndrome Outcome Study was to evaluate the short-term and long-term effectiveness of standard versus minimal-contact CBT on IBS symptoms. The study also sought to identify the factors which determine whether or not CBT will be practical and cost-effective.

Global improvement of IBS symptoms was assessed at regular intervals following the treatment period. Patients were also evaluated to determine the impact of the treatment on their quality of life.

Inclusion Criteria: Study participants were age 18 to 70 years old; able to read, speak, and understand English at a sixth grade level or higher; had moderately severe IBS symptoms based on the Rome III criteria; agreed to not take medication, not start any new medication, or only take a stable dose of required medication during the pre-treatment period; had access to a telephone; and able to adhere to the protocol requirements and complete all assessments and questionnaires.

Exclusion Criteria: Individuals were excluded from the study if their GI symptoms were due to medication use, biochemical or structural abnormalities, abdominal surgery, or other GI illnesses/conditions; they were currently receiving psychotherapy for IBS; had been diagnosed or treated for a malignancy, except localized basal or squamous cell carcinomas of the skin, in the last five years; had an infection or other condition/disorder that would interfere with study procedures; received antibiotic treatment for IBS symptoms at least three months prior to baseline assessment; or they were unable to follow the study protocol or complete the necessary assessments and evaluations.

Based on patient assessments following the completion of treatment, IBSOS determined that minimal-contact CBT delivered better results than supportive counseling. During follow-up visits, the rate of patients who reported improvements in their IBS symptoms was significantly higher in the minimal-contact CBT group compared to the IBS education group. It was also determined, through formal equivalence testing, that the effects of minimal-contact CBT were comparable to standard CBT. These findings suggest that in randomized trials, minimal-contact CBT can be more beneficial than supportive counseling and education in IBS patients with moderate to severe symptoms.