Irritable bowel syndrome (IBS) is considered a biopsychosocial disorder resulting from a combination of 3 interacting mechanisms: psychosocial factors, altered motility and transit, which may reflect severity of bowel dysfunction, and increased sensitivity of the intestine or colon. In other words, mechanism in IBS is biopsychosocial disorders; psychosocial factors, altered motility, and heightened sensory function. Understanding the brain-gut axis is the key to the eventual development of effective therapies for IBS.