We welcome the conclusion by Creed (Gut 2006;55:1065–7) that citalopram leads to clinical improvement in irritable bowel syndrome (IBS) uncomplicated by psychiatric illness¹ by targeting psychological processes. The implicit assumption is that psychological disturbance is fundamental to IBS, irrespective of psychiatric comorbidity.

This is consistent with a previously proposed disease model for functional gastrointestinal disorders,² which suggested that dominant, shared psychological disturbance provides the best explanation for the very high overlap between IBS, other functional disorders (gastrointestinal and otherwise) and depression/anxiety. The model also explained how depression and IBS can wax and wane independently, and predicted that the response of non-psychiatric IBS to selective serotonin reuptake inhibitor antidepressants would be similar to the response of depressive disorders to selective serotonin reuptake inhibitors.

We also welcome the author’s identification of abnormal illness beliefs as the principal psychological pathology. Evidence suggesting that these beliefs are causative in IBS³ has recently been supported by the demonstration that cognitive behaviour therapy, which targets these beliefs, leads to clinical improvement. Further scrutiny of these beliefs could be the key to understanding the nature and importance of the central pathology of IBS and other functional disorders.