Background & Aims
Visceral pain is an under-recognized clinical and societal problem [6, 7]. Psychological factors play a role in the pathophysiology and treatment [3], as underscored by evidence from placebo research demonstrating pain relief based on positive expectations [11]. Negative expectations, i.e. nocebo effects, likely to be crucial to the clinical reality of patients, have rarely been studied in visceral pain. Considering the differences between visceral and somatic pain regarding perception and responses, such as visceral pain being more salient and fear-inducing [2, 9, 10], research on clinically relevant visceral pain models is needed to complement the nocebo knowledge from the somatic pain domain.
Therefore, we examined both the separate and combined effects of negative expectations formed by information from healthcare providers (instruction) and by treatment experiences (conditioning) [5], respectively, using a multiple threat paradigm comprising visceral and somatic pain stimuli.
Methods
This experimental randomized controlled trial [1] assessed nocebo effects in response to a series of individually calibrated rectal distensions and thermal cutaneous stimuli that were matched to perceived pain intensity prior to a baseline. Negative expectations were induced by elements of doctor-patient communication (i.e., instruction) and/or by a negative conditioning experience using surreptitiously increased thermal pain in the experience phase. Accordingly, the design included the factors “treatment instruction” (negative vs. neutral) and “treatment experience” (negative vs. neutral), with healthy volunteers (total N=102) randomized into four groups. We compared the groups with respect to overall perceived pain unpleasantness, assessed separately for each pain modality using visual analog scales (VAS; “not unpleasant (0) and “extremely unpleasant” (100)).
Results
Despite successful initial matching, perceived pain unpleasantness was consistently higher for visceral pain (p < 0.001), but did not differ between experimental groups. For the somatic modality, increased pain ratings were observed in the experiential phase in the group with the combination of negative instruction and negative experience (36.5±25.4 vs. 71.0±22.5; NRS±SD; p < 0.001) compared to the control/control group and in the group with control instruction and negative experience (53.4±30.3 vs. 71.0±22.5; NRS±SD; p = 0.023), indicating a nocebo effect based on the negative instruction. Hence, the combination of negative instruction and negative experience in the experience phase resulted in similarly high ratings for the somatic and visceral modalities.
Conclusions
These results in healthy participants in a translational nocebo paradigm show distinct differences between visceral and somatic pain. Unpleasantness was consistently shown to be significantly higher for visceral than for somatic stimuli across all groups. For the somatic modality to be perceived as unpleasant as visceral pain, a combination of negative instruction and negative experience was required highlighting the inherent threat of visceral pain. Interestingly, however, the nocebo mechanisms led to significant changes in somatic pain ratings. Our results demonstrate differential pain modulation by negative expectations in visceral and somatic pain, which need to be further investigated for personalized and pain modality-specific treatment approaches for different chronic pain conditions.
References
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Presenting Author
Jana Aulenkamp
Poster Authors
Jana Luisa Aulenkamp, M.D.
Dr. med.
Clinic for Anesthesiology and Intensive Care, University Hospital Essen, Germany
Lead Author
Robert Jan Pawlik
Dr.
Lead Author
Catrin Guddat
Lead Author
Adriane Icenhour
Prof. Dr.
Lead Author
Sigrid Elsenbruch
Prof. Dr.
Lead Author
Topics
- Specific Pain Conditions/Pain in Specific Populations: Post-surgical/Post-traumatic Chronic Pain