(236) Impaired conditioned pain modulation in youth with functional abdominal pain

Abstract

Functional abdominal pain (FAP) is associated with enhanced pain responsiveness. Although impaired conditioned pain modulation (CPM) characterizes adults with a variety of chronic pain conditions, relatively little is known about CPM in youth with FAP. The present study assessed CPM to evoked thermal pain in 140 youth (ages 10 to 17), 63 of whom had FAP and 77 of whom were healthy controls. Multilevel models demonstrated weaker CPM effects in FAP than healthy youth, as evident in slower within-person decreases in pain ratings during the conditioning phase. Weaker CPM effects were associated with greater somatic symptom severity and functional disability. Pain responses in FAP youth were heterogeneous, with 43% of youth showing an unexpected increase in pain ratings during the conditioning phase, suggesting sensitization rather than CPM-related pain inhibition. These findings highlight directions for future research on the emergence and maintenance of FAP in youth. Keywordsfunctional abdominal pain; FAP; CPM; DNIC; adolescents Functional abdominal pain (FAP) refers to either episodic or continuous abdominal pain that remains medically unexplained despite thorough physical examination [36]. According to a recent meta-analysis, FAP is common in youth, with a worldwide pooled prevalence rate of 13.5% [18]. Many youth with FAP either meet current Rome III criteria for functional Corresponding Author: Uma Rao, M.D., Address: University of Tennessee, CMHSRC, 122 Henson Hall, 1618 West Cumberland Avenue, Knoxville, Phone: (865) FAX: (865) 974-1662, urao@utk.edu. HHS Public Access Author Manuscript Author ManuscriptAuthor ManuscriptAuthor Manuscript gastrointestinal disorders, including irritable bowel syndrome (IBS), functional dyspepsia and abdominal migraine [2], or are at increased risk for developing functional gastrointestinal disorders over time [48]. FAP in youth is associated with significant functional disability, reflected in part by school absences [36], and is often persistent despite frequent utilization of health care services [13]. Although a variety of biological and psychosocial factors [48,49] have been implicated in the development and maintenance of FAP in youth, little is known about the impact of altered pain modulatory systems.Experimental pain responses, which may index functioning in pain modulatory systems, have proven useful as biomarkers of risk for chronic pain by discriminating clinical pain populations from healthy controls, correlating with changes in clinical pain, and predicting the development of chronic pain [11]. Pro-nociceptive pain modulation profiles are characterized by decreased inhibition and/or increased temporal summation to evoked pain [53]. One experimental method used to detect dysfunction in descending inhibitory pain modulatory systems is conditioned pain modulation (CPM; previously termed diffuse noxious inhibitory controls or DNIC), which refers to a reduction in perceived pain intensity for a test stimulus during application of a conditioning stimulus to...