V. Stress and irritable bowel syndrome.

Different types of stress play important roles in the onset and modulation of irritable bowel syndrome (IBS) symptoms. The physiological effects of psychological and physical stressors on gut function and brain-gut interactions are mediated by outputs of the emotional motor system in terms of autonomic, neuroendocrine, attentional, and pain modulatory responses. IBS patients show an enhanced responsiveness of this system manifesting in altered modulation of gastrointestinal motility and secretion and in alterations in the perception of visceral events. Functional brain imaging techniques are beginning to identify brain circuits involved in the perceptual alterations. Animal models have recently been proposed that mimic key features of the human syndrome.