Endogenous inhibition of somatic pain is impaired in girls with irritable bowel syndrome compared with healthy girls

Abstract

Endogenous pain inhibition is often deficient in adults with chronic pain conditions including irritable bowel syndrome (IBS). It is unclear whether deficiencies in pain inhibition are present in young children with IBS. The present study compared endogenous pain inhibition, somatic pain threshold, and psychosocial distress in young girls with IBS versus controls. Girls with IBS did not show significant endogenous pain inhibition of heat pain threshold during a cold-pressor task in contrast to controls, who had significant pain inhibition. Girls with IBS did not differ from peers on measures of somatic pain but had more symptoms of depression, somatization, and anxiety than controls. When psychological variables were included as covariates, the difference in pain inhibition was no longer significant, although poor achieved power limits interpretation of these results. Higher-order cognitive processes including psychological variables may be contributing to observed pain inhibition. In girls with IBS, pain inhibition was positively related to the number of days without a bowel movement. To our knowledge, this is the first study to demonstrate deficiencies of endogenous pain inhibition in young children with IBS. Findings have implications for better understanding of onset and maintenance of IBS and other chronic pain conditions.

Perspective: This study found that young girls with IBS have deficient endogenous pain inhibition compared to healthy girls, which is consistent with the literature on adults. This information can facilitate clinicians in identification of risk factors for onset/maintenance of IBS and other chronic pain conditions.

Keywords: Diffuse noxious inhibitory controls; children; conditioned pain modulation; endogenous pain modulation; irritable bowel syndrome.

Figure 1. Endogenous Pain-Inhibition

Positive number represents pain inhibition and negative number represents pain facilitation. IBS is irritable bowel syndrome. Solid grey bars represent endogenous pain-inhibition effect for each group without any covariates. Middle (lined) bars represent endogenous pain-inhibition effect with significant parent-report (PR) psychological variables (child anxiety, child depression, and child somatization) included as covariates. White bars represent endogenous pain-inhibition effect with significant child-report (CR) psychological variables (anxiety & somatization) included as covariates. * indicates significance at p<.05. Although results are no longer significant after covariates are included, a similar pattern of results is present.

Figure 2. Pain Inhibition and Days without a Bowel Movement

Positive change score represents pain inhibition and negative change score represents pain facilitation. IBS is irritable bowel syndrome.