A model of irritable bowel syndrome (IBS) and its associations with other clinical, intestinal, extra-intestinal and psychiatric conditions. For each of the listed disorders, overlap with IBS symptoms has been reported in the literature11. The different components should be viewed as layers of complexity: the IBS subtypes are part of the group of functional bowel disorders, these are part of all kinds of functional disorders and these again are part of a `layer' of psychiatric disorders. GERD, gastroesophageal reflux disease; IBS-C, IBS with constipation; IBS-D, IBS with diarrhoea; IBS-M, mixed-type IBS; IBS-U, unsubtyped IBS; PMS, premenstrual syndrome.