Background & Aims

Observing effective pain treatment in others may trigger anticipatory brain processes, which reduce pain.1–3 Previous studies have suggested that social learning and observation influence placebo hypoalgesia.1,2 We found race and participant-experimenter race concordance to have a significant impact on the placebo hypoalgesia induced by conditioning.4 However, no study examined the impact of race and participant-experimenter race concordance on the placebo effects. The mechanisms underlying the influence of race/ethnicity on placebo effects remain unclear. Aiming at filling this gap, we examined the impact of race, race concordance, and racial implicit bias on the placebo effect induced by social learning.

Methods

In three independent studies, 116 healthy participants went through a social learning paradigm.1,2 Following an observation phase, each participant underwent a self-experience phase. We measured different markers of race/ethnicity. The implicit racial bias was measured with the Implicit Association Test (IAT). The race categories were White (W), Black/African American (B/AA), Asian (A), American Indian, and other race. The demonstrator was W, and the experimenters were W, B/AA, and A. We therefore limited the analyses to W (n=52), B/AA (n=33) and A (n=30) participants. Pain ratings were assessed by a Visual Analogue Scale (VAS) ranging from 0=no pain to 100=maximum tolerable pain. Placebo effects were defined as the difference between pain ratings for placebo and control trials. For this multi-study project, we used a general linear model to examine the direct and interaction effects of race, race concordance and IAT on the placebo effect, and the mediation/moderation effect of IAT.

Results

Overall, we found a trend towards a main effect of W, B/AA and A races (p=0.089). There were interaction effects of race and race concordance on socially induced placebo effects for W and A only. Specifically, when the experimenter’s race was concordant, W and A showed similar placebo effects (mean VAS diff.=0.985 sem=4.7, p=0.833, Bonferroni corrected). On the contrary, when there was no participant-experimenter concordance, A participants had greater placebo effects than W participants (mean VAS diff.=10.5 sem=4.8, p=0.032, Bonferroni corrected). W participants had stronger implicit bias towards W individuals compared to A participants (mean IAT difference=0.209, p=0.039, Bonferroni corrected). We found that the effect of race on placebo effects in A participants was moderated by a higher implicit bias towards W people (B=0.025, p=0.30; B=0.549, p=0.014). This was not observed for W participants. These results were consistently found across three different social learning protocols.

Conclusions

This is the first study investigating the racial component on socially induced placebo effects. These results suggest that examining the direct effect of race and racial concordance might not be enough to grasp the complexity of their influence on socially induced placebo effects. The influence of race, affecting specifically W and A participants, is different when there is or not participant-experimenter race concordance. Further, this relationship is moderated by the participants’ implicit racial bias. Therefore, future research should evaluate the impact of implicit bias along with race-concordance in any placebo as well as pain studies.

References

1.Raghuraman, N. et al. Neural and behavioral changes driven by observationally-induced hypoalgesia. Sci. Rep. 9, 19760 (2019).
2.Schenk, L. A., Krimmel, S. R. & Colloca, L. Observe to get pain relief: current evidence and potential mechanisms of socially learned pain modulation. Pain 158, 2077–2081 (2017).
3.Bajcar, E. A. & B?bel, P. How Does Observational Learning Produce Placebo Effects? A Model Integrating Research Findings. Front. Psychol. 9, (2018).
4.Okusogu, C. et al. Placebo hypoalgesia: racial differences. Pain 161, 1872–1883 (2020).

Presenting Author

Carmen-Edith Bellei-Rodriguez

Poster Authors

Carmen-Edith Bellei-Rodriguez

Ps. ED., Ph.D.

University of Maryland Baltimore

Lead Author

E-mail

Nandini Raghuraman

MS

University of Maryland, Baltimore

Lead Author

E-mail

Jewel Clark

University of Maryland Baltimore

Lead Author

E-mail

Roni Shafir

Ph.D.

University of Maryland, Baltimore

Lead Author

E-mail

Lakota Watson

University of Maryland Baltimore

Lead Author

E-mail

Yang Wang

School of Nursing, University of Maryland, Baltimore

Lead Author

E-mail

Luana Colloca and PhD

Placebo Beyond Opinions Center, University of Maryland School of Nursing, MD, USA

Lead Author

E-mail

Topics

  • Racial/Ethnic/Economic Differences/Disparities