Background & aims: Rectal pain sensitivity has been called a biological marker for irritable bowel syndrome, but this conclusion may be premature. This article is a critical review of the evidence for psychological influences on perception.
Methods: The world literature accessible 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 thresholds are not correlated with anxiety or depression. Evidence favoring psychological influences on perception is that patients with the irritable bowel syndrome rate even sham distentions as more painful, and when perception tests that minimize psychological influences are used, they have normal sensory thresholds. Also, stress alters sensory thresholds. Sensitization by repeated distention has been cited as evidence of a biological basis for hyperalgesia, but it is not unique to patients with irritable bowel. Brain imaging shows that different regions are activated by painful distention in patients with irritable bowel syndrome, but this is consistent with psychological influences on perception.
Conclusions: Psychological factors influence pain thresholds in patients with the irritable bowel syndrome. Two cognitive traits, selective attention to gastrointestinal sensations and disease attribution, may account for increased pain sensitivity.