Women who suffer from irritable bowel syndrome may respond to pain signals differently from other women, leaving them more vulnerable to the intestinal discomfort that characterizes the disease.
That is the finding of researchers who exposed women with and without the syndrome to mildly painful stimuli and then watched how their brains responded using a functional M.R.I. machine. The study appeared Jan. 9 in The Journal of Neuroscience.
The researchers focused on the brain's ability to tamp down its response to pain if it knows that it is coming and that it will not be too severe. (It also does this if the pain will bring about a benefit, like the removal of a splinter.)
When women without irritable bowel syndrome were about to be given the pain stimuli after a warning, their M.R.I. showed their brains stepping down the brain response. But the women with the condition appeared unable to do so.
The finding suggests that people with the syndrome may suffer in part because they handle pain differently.
"That does not mean the pain is less real," the lead author of the study, Steven Berman of the University of California, Los Angeles, wrote in an e-mail message.