2017 Volume 57 Issue 4 Pages 335-342
Stress is one of important issues to be solved by psychosomatic researchers in the 21st century. Irritable bowel syndrome (IBS) is a prototype of functional gastrointestinal disorders (FGIDs) which are one of typical stress-related disorders. IBS patients usually show dysfunction of the colon and/or small bowel which are/is evoked by the efferent signal from the brain. Corticotropin-releasing hormone (CRH) is released from the paraventricular nucleus (PVN) of the hypothalamus by stress loading and it switches exaggerated colonic motility by way of sacral parasympathetic outflow. Released CRH also degranulates mast cells, increased permeability of the gut mocosa, and cause visceral hypersensitivity. Visceral hypersensitivity is important pathophysiology of IBS with dysregulation of brain-gut interactions. Dysregulation of regional brain at visceral stimulation is seen in the anterior cingulate cortex, mid cingulate cortex, insula, amygdala, hippocampus, hypothalamus, dorsolateral prefrontal cortex, medial prefrontal cortex, orbitofrontal cortex, striatum, and periaqueductal gray matter in IBS patients. Gut microbiota is also involved in the pathophysiology of IBS and composition of gut microbiota is influenced by psychosocial stress. IBS is highly related to depression, anxiety, and alexithymia. These features are based on molecular and neural changes. In another words, functional (and psychosomatic) disorders would have structural and organic changes which can be detected by advanced technology. Therefore, fine and quantitative measurements are important to explore pathogenesis of stress-related disorders. Severe stress induces methylation of the promoter gene of the glucocorticoid receptors and impair negative feedback of CRH systems and pathological hypothalamic-pituitary-adrenocortical axis. IBS research provides typical phenomena of gene-environmental interaction and plausible candidate genes including CRH receptor genes for IBS has been detected. Advanced therapies including psychopharmacotherapy, psychotherapy, and neuromodulation are developing. To cope with IBS, it is important to find the law of stress and brain-gut interactions. Moreover, practical use of psychosomatic approach including cognitive behavior therapy is recommended for clinicians. Similar activities to find the law of stress and brain-gut interactions can be applicable to the other areas of medicine.
