• Junie S Carriere, Marc Olivier Martel, Samantha M Meints, Marise C Cornelius, and Robert R Edwards.
• Department of Anesthesiology, Brigham and Women's Hospital Pain Management Center, Harvard Medical School, Chestnut Hill, Massachusetts.
• Eur J Pain. 2019 Apr 1; 23 (4): 800-811.

BackgroundPain expectancies are associated with altered pain sensitivity in individuals with chronic pain. However, little is known about the processes by which pain expectancies impact pain processing. This study assessed the association between pain expectancies and temporal summation (TS) of pain, and examined whether pain catastrophizing mediated this association.MethodsIn this cross-sectional study, participants (437 chronic low back pain [CLBP] patients, 115 controls) completed self-report measures of pain intensity, pain expectancies and pain catastrophizing before undergoing psychophysical pain-testing procedures designed to assess mechanical TS of mechanical pain. Pearson's correlations examined the associations between study variables in CLBP patients and controls. Bootstrapping mediation analyses assessed the mediating role of pain catastrophizing on the association between pain expectancies and TS of pain.ResultsTemporal summation of pain was significantly associated with pain expectancies (r = 0.113) and pain catastrophizing (r = 0.171) in CLBP patients. Results of mediation analyses revealed that pain catastrophizing mediated the relationship between pain expectancies and TS of pain in CLBP patients (ab = 0.309, 95% CI = 0.1222-0.5604), but not in healthy controls (ab = -0.125, 95% CI = -0.5864 to 0.0244).ConclusionsThe findings from this study suggest that compared to controls, CLBP patients show increased sensitivity to mechanical pain procedures and enhanced pain-facilitatory processing, proving further evidence for changes in central nervous system pain processing in CLBP patients. Our results also suggest that pain catastrophizing may be the mechanism by which pain expectancies are associated with TS of pain in CLBP patients.SignificanceIndividuals with chronic low back pain who expect higher levels of pain and catastrophize about their pain are more likely to experience altered pain sensitivity. Our results point to catastrophizing as a mechanism of action through which psychological factors may operate and lead to the development and maintenance of chronic low back pain.© 2018 European Pain Federation - EFIC®.

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