The irritable bowel syndrome (IBS), which is characterized by abdominal pain and altered bowel habits, is the most common gastrointestinal disorder, affecting 9.4 percent of the population. Fifty to 60 percent of IBS patients report pain at abnormally low volumes of rectal distention, suggesting that visceral hyperalgesia may be the mechanism for IBS. A cognitive behavioral model is presented which accounts for increased pain sensitivity in IBS by two hypotheses: (1) Two cognitive traits--selective attention on gastrointestinal sensations and attribution of disease significance to these sensations--are the mechanisms by which stress and other factors influence pain perception. (2) Childhood social learning in the form of increased attention for somatic complaints and modeling of sick role behavior by parents, is the most important determinant of selective attention and disease attribution. The differential recall of previously memorized words, depending on their content, will be used to develop a test for selective attention. Words describing gastrointestinal sensations plus control words describing respiratory sensations and neutral words will be tested for a prior probability of recall by healthy subjects. Then IBS patients, patients with lactose malabsorption (an enzyme deficiency producing chronic gastrointestinal symptoms similar to IBS), patients with asthma, and healthy controls will memorize these words, and 15 minutes later will be tested for recall. Other techniques for assessing selective attention which will be compared to the recall task are the Stroop Color Test and recognition of words in the above categories presented briefly by a tachistoscope. The test of disease attribution will be developed by presenting the same gastrointestinal and respiratory sensations and asking subjects to rate whether they could be symptoms of disease. After developing valid and reliable measures, new samples of IBS patients, lactose intolerant patients, and controls will complete these tests of reinforcement and modeling of gastrointestinal-related sick role behavior and tests of rectal distention pain thresholds. A subsequent study will determine whether experimental stress increases pain sensitivity and progressive muscle relaxation decreases pain sensitivity in IBS patients, and whether these psychological influences on perceptions are associated with changes in selective attention to gastrointestinal sensations.
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