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Placebo analgesia in patients with functional and organic abdominal pain: a fMRI study in IBS, UC and healthy volunteers
  1. Julia Schmid1,
  2. Jost Langhorst2,
  3. Florian Gaß1,2,
  4. Nina Theysohn3,
  5. Sven Benson1,
  6. Harald Engler1,
  7. Elke R Gizewski4,
  8. Michael Forsting3,
  9. Sigrid Elsenbruch1
  1. 1Institute of Medical Psychology and Behavioral Immunobiology, University Hospital Essen, University of Duisburg-Essen, Essen, Germany
  2. 2Integrative Gastroenterology, Clinic for Internal and Integrative Medicine, Kliniken Essen-Mitte, Essen, Germany
  3. 3Institute of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, University of Duisburg-Essen, Essen, Germany
  4. 4Clinic for Neuroradiology, Medical University Innsbruck, Innsbruck, Austria
  1. Correspondence to Professor S Elsenbruch, Institute of Medical Psychology and Behavioral Immunobiology, University Hospital Essen, University of Duisburg-Essen, Hufelandstr 55, Essen 45122, Germany; sigrid.elsenbruch{at}uk-essen.de

Abstract

Objective Understanding the neural circuitry of placebo analgesia in the context of visceral pain is increasingly important given evidence of clinical benefit of placebo treatment in IBS. This functional MRI study addressed placebo analgesia in IBS, UC and healthy control (HC) volunteers.

Design Painful rectal distensions were delivered in N=17 patients with IBS , N=15 patients with UC in remission, and sex-matched and age-matched HCs in an adaptation phase followed by intravenous application of saline combined with either positive instructions of pain relief (placebo) or neutral instructions (control). Neural activation during cued-pain anticipation and pain was analysed along with ratings of expected and perceived pain and measures of negative affectivity and salivary cortisol concentrations. Correlational analyses between placebo analgesia responses and negative affect were accomplished.

Results HC and UC revealed significant pain inhibition during placebo analgesia, as evidenced by reduced neural activation in pain-related brain areas. In contrast, patients with IBS failed to effectively engage neural downregulation of pain, as evidenced by the absence of placebo-induced changes in distension-induced brain activation, resulting in a significant group difference in the cingulate cortex compared with HC. Depression scores correlated with weaker placebo analgesia, whereas state and trait anxiety were not associated.

Conclusions Patients with IBS failed to effectively engage neural downregulation of rectal distension-induced pain during placebo analgesia, indicating a specific deficit in cognitive pain inhibition, which may in part be mediated by depression.

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