Objectives: Symptoms in irritable bowel syndrome (IBS) patients are sensitive to psychological stressors. These effects may operate through an enhanced responsiveness of the emotional motor system, a network of brain circuits that modulate arousal, viscerosomatic perception, and autonomic responses associated with emotional responses, including anxiety and anger. The aim of this study was to test the primary hypothesis that IBS patients show altered perceptual responses to rectal balloon distention during experimentally induced psychological stress compared with healthy control subjects.
Methods: A total of 15 IBS patients (nine women and six men) and 14 healthy controls (seven women and seven men) were studied during two laboratory sessions: 1) a mild stress condition (dichotomous listening to two conflicting types of music), and 2) a control condition (relaxing nature sounds). The stress and relaxation auditory stimuli were delivered over a 10-min listening period preceding rectal distentions and during the rectal distentions but not during the distention rating process. Ratings of intensity and unpleasantness of the visceral sensations, subjective emotional responses, heart rate, and neuroendocrine measures (norepinephrine, cortisol, adrenocorticotropic hormone [ACTH], and prolactin) were obtained during the study.
Results: IBS patients, but not healthy controls, rated the 45-mm Hg visceral stimulus significantly higher in terms of intensity and unpleasantness during the stress condition compared with the relaxation condition. IBS patients also reported higher ratings of stress, anger, and anxiety during the stress compared with the relaxing condition, whereas controls had smaller and nonsignificant subjective responses. Heart rate measurements, but not other neuroendocrine stress measures, were increased under the stress condition in both groups.
Conclusion: These findings confirm the hypothesis of altered stress-induced modulation of visceral perception in IBS patients.