The Irritable Bowel Syndrome Outcome Study (IBSOS): Rationale and design of a randomized, placebo-controlled trial with 12month follow up of self- versus clinician-administered CBT for moderate to severe irritable bowel syndrome

Irritable bowel syndrome is a common, oftentimes disabling, gastrointestinal disorder whose full range of symptoms has no satisfactory medical or dietary treatment. One of the few empirically validated treatments includes a specific psychological therapy called cognitive behavior therapy which, if available, is typically administered over several months by trained practitioners in tertiary care settings. There is an urgent need to develop more efficient versions of CBT that require minimal professional assistance but retain the efficacy profile of clinic based CBT. The Irritable Bowel Syndrome Outcome Study (IBSOS) is a multicenter, placebo-controlled randomized trial to evaluate whether a self-administered version of CBT is, at least as efficacious as standard CBT and more efficacious than an attention control in reducing core GI symptoms of IBS and its burden (e.g. distress, quality of life impairment, etc.) in moderately to severely affected IBS patients. Additional goals are to assess, at quarterly intervals, the durability of treatment response over a 12. month period; to identify clinically useful patient characteristics associated with outcome as a way of gaining an understanding of subgroups of participants for whom CBT is most beneficial; to identify theory-based change mechanisms (active ingredients) that explain how and why CBT works; and evaluate the economic costs and benefits of CBT. Between August 2010 when IBSOS began recruiting subjects and February 2012, the IBSOS randomized 171 of 480 patients. Findings have the potential to improve the health of IBS patients, reduce its social and economic costs, conserve scarce health care resources, and inform evidence-based practice guidelines.