IS RECTAL PAIN SENSITIVITY A BIOLOGICAL MARKER FOR IRRITABLE-BOWEL-SYNDROME - PSYCHOLOGICAL INFLUENCES ON PAIN PERCEPTION

Background & Aims: Rectal pain sensitivity has been called a biologica l marker for irritable bowel syndrome, but this conclusion may be prem ature. This article is a critical review of the evidence for psycholog ical influences on perception. Methods: The world literature accessibl e through Index Medicus from 1973 to 1997 was systematically reviewed. Results: Evidence favoring a biological basis for pain sensitivity is that two thirds of patients report pain at abnormally low thresholds of rectal distention despite normal somatic pain thresholds. Pain thre sholds are not correlated with anxiety or depression. Evidence favorin g psychological influences on perception is that patients with the irr itable bowel syndrome rate even sham distentions as more painful;and w hen perception tests that minimize psychological influences are used, they have normal sensory thresholds. Also, stress alters sensory thres holds. Sensitization by repeated distention has been cited as evidence of a biological basis for hyperalgesia, but it is not unique to patie nts with irritable bowel. Brain imaging shows that different regions a re activated by painful distention in patients with irritable bowel sy ndrome, but this is consistent with psychological influences on percep tion. Conclusions: Psychological factors influence pain thresholds in patients with the irritable bowel syndrome. Two cognitive traits, sele ctive attention to gastrointestinal sensations and disease attribution , may account for increased pain sensitivity.