Ethnic Differences in Experimental Pain Responses Following a Paired Verbal Suggestion With Saline Infusion: A Quasiexperimental Study.


Letzen JE(1), Dildine TC(2)(3), Mun CJ(1), Colloca L(4)(5)(6), Bruehl S(7), Campbell CM(1).
Author information:
(1)Department of Psychiatry and Behavioral Science, Johns Hopkins University School of Medicine, Nathan Shock Drive, Suite, Baltimore, MD, USA.
(2)National Center for Complementary and Integrative Health, National Institutes of Health, Bethesda, MD, USA.
(3)Department of Clinical Neuroscience, Karolinska Institutet, Solna, Sweden.
(4)Department of Pain and Translational Symptom Science, School of Nursing, University of Maryland, Baltimore, MD, USA.
(5)Departments of Anesthesiology and Psychiatry, School of Medicine, University of Maryland, Baltimore, University of Maryland, Baltimore, MD, USA.
(6)Center to Advance Chronic Pain Research, University of Maryland, Baltimore, MD, USA.
(7)Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN, USA.


BACKGROUND: Ethnic differences in placebo and nocebo responses are an important, yet underresearched, patient factor that might contribute to treatment disparities. PURPOSE: The purpose of this study was to examine ethnic differences in pain trajectories following a verbal suggestion paired with a masked, inert substance (i.e., saline). METHODS: Using a quasiexperimental design, we examined differences between 21 non-Hispanic Black (NHB) participants and 20 non-Hispanic White (NHW) participants in capsaicin-related pain rating trajectories following a nondirectional verbal suggestion + saline infusion. All participants were told that the substance would "either increase pain sensation, decrease it, or leave it unchanged." A spline mixed model was used to quantify the interaction of ethnicity and time on ratings. RESULTS: There was a significant Ethnicity × Time interaction effect (β = -0.28, p = .002); NHB individuals reported significantly greater increases in pain following, but not before, the verbal suggestion + saline infusion. Sensitivity analyses showed no change in primary results based on differences in education level, general pain sensitivity, or condition order. CONCLUSIONS: The present results showed ethnic differences in pain response trajectories following a verbal suggestion + saline infusion and suggest that future research rigorously examining possible ethnic differences in placebo/nocebo responses is warranted.