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Mechanisms Related to IBS

Study Description:

Irritable Bowel Syndrome (IBS) is a common chronic disorder which causes abdominal pain and discomfort.  IBS is associated with diarrhea or constipation or both. The purpose of this study is to look at the association of the nervous system with pain or discomfort in women with IBS and those without IBS.  We will also look at how symptoms, stress and genes influence the results. Our goal is to make progress in understanding the causes of IBS and finding effective treatments.

There are three or four parts to this study:

  • The volunteer will come to the university where a nurse will interview her, take a health history, and draw a blood sample.  After the interview the volunteer will wear a heart rate monitor for 12 hours and do a mental health interview by telephone.
  • At home she will keep a symptom diary for 4-5 weeks beginning with her next menses;
  • Testing Phase 1:
    • On one day we will test her response to 7 seconds of heat on her arm and drinking water for 5 minutes or until full. This test visit will take about 1½ hour.
    • On the second test day the volunteer will listen to quick bursts of white noise that cause her eyes to blink. We will also deliver a mild electrical stimulus to her abdomen to cause a muscle contraction. This test visit takes about 1½ -2 hours.
  • Testing Phase 2:
    • Only women with IBS may volunteer for the fourth test one month later.
    • The volunteer will come to the UW Clinical Research Center in the UW Medical Center, down the hall from the School of Nursing. 
    • The research nurse will administer 2 rectal sensitivity tests that last about 20 minutes including rest before and after each test.
    • The testing session will last about 4 hours.
  • Visits vary in time needed from 1½ to 4 hours.
  • We will collect a urine sample at the first test visit and 3 saliva samples at each Phase 1 test visit and 4 saliva samples at the Phase 2 test visit.
  • It will take up to 2 months to complete parts 1-3 or 3 months to complete all 4 parts: the initial visit, 2 (or 3) test visits, and diary.
  • There are no medications involved in this study.
  • The volunteer can stop any of these tests at any time.

Eligibility Criteria:

  • Volunteers must be female, 18-45 years old.
  • This study accepts women with a diagnosis of IBS and also healthy volunteers.
  • IBS Group: The women must have a prior diagnosis of IBS made by a primary health care provider and current symptoms of abdominal pain or discomfort that are relieved by a bowel movement or associated with a change in stool consistency or frequency. They must have had a diagnosis of IBS for at least 6 months prior to starting the study.
  • Comparison Group: The women do not meet criteria for any functional GI disorder.

Women are excluded if they:

  • Have a history of an organic GI disease (e.g., inflammatory bowel disease, bowel resection), co-morbid conditions that make it hard to assess IBS symptoms; or have diabetes, heart disease, thyroid disease, bipolar disease or are psychotic;
  • Are currently taking daily anti-diarrhea and anti-spasmodic medications (laxatives are acceptable if taken as prescribed or as recommended for over-the-counter medications);
  • Consume more than 2 servings of alcohol containing beverages every day;
  • Are pregnant or planning to become pregnant during the study period or;
  • Have a diagnosis of chronic constipation.


Health Sciences Building, University of Washington, Seattle, Washington


Volunteers will receive up to $340 if they finish all parts of the study, and an additional $250 plus a book, Master Your IBS for completing the rectal sensitivity test.

Principal Investigator:

Margaret Heitkemper, PhD, RN

For further information about this study, please contact:

Pamela Barney, MN, ARNP


(206) 685-5660