Irritable Bowel Syndrome, or IBS, is a condition that concerns the large intestine. It can cause diarrhea, constipation or both. Its symptoms are very painful and for the people who suffer from IBS, it can be disruptive to their lives. Many people find themselves scheduling their days around their IBS symptoms. Irritable Bowel Syndrome affects up to 20% of American adults at some point in their lives.