[Psychosocial factors and visceral hypersensitivity in irritable bowel syndrome]

Most studies provide strong support for an etiologic role of stressful life events in irritable bowel syndrome (IBS). Consistent with the observations in both patients and doctors that psychosocial disturbances seem to precede the onset or exacerbation of gut symptoms, researches have consistently found high levels of emotional distress in a proportion of patients with IBS and other functional gastrointestinal disorders. Moreover, a variety of other potentially psychiatric diseases such as anxiety, depression, and sleep disorder also coexist frequently with IBS. In recent literatures, some studies have shown altered mechanoelastic properties such as colonic tone, compliance, and accommodation. The demonstrated differences in colonic compliance and accommodation suggest peripheral neuromuscular substrate contributing to the pathogenesis of IBS. However, until now, attention has focused on the disturbances of visceral hypersensitivity rather than on gastrointestinal motor function as a hallmark of IBS pathophysiology. But not all IBS patients show decreased rectosigmoid pain thresholds. Recent advances in brain imaging have allowed investigators to measure changes in regional cerebral blood flow during stimulation. Those methods have extended our understanding of brain function and brain-gut interaction. IBS is characterized by hypersensitivity to visceral sensation and augmented response to stress. Studies on the disorders of sensori-motor function have also contributed to understand the knowledge of neurotransmitters involved in the function of the enteric nervous system and to identify targets for the development of new treatments for IBS.