Real Bodies Not Required? Placebo Analgesia and Pain Perception in Immersive Virtual and Augmented Reality

Pain represents an embodied experience, wherein inferences are not only drawn from external sensory inputs, but also from bodily states. Previous research has demonstrated that a placebo administered to an embodied rubber hand can effectively induce analgesia, providing first evidence that placebos can work even when applied to temporarily embodied, artificial body parts. Using a heat pain paradigm, the present study investigates placebo analgesia and pain perception during virtual embodiment. We examined whether a virtual placebo (a sham heat protective glove) can successfully induce analgesia, even when administered to a virtual body. The analgesic efficacy of the virtual placebo to the real hand (augmented reality setting) or virtual hand (virtual reality setting) was compared to a physical placebo administered to the own, physical body (physical reality setting). Furthermore, pain perception and subjective embodiment were compared between settings. In this mixed design experiment, healthy participants (n = 48) were assigned to either an analgesia-expectation or control-expectation group, where subjective and objective pain was measured at pre-and post-intervention time points. Results demonstrate that pre-intervention pain intensity was lower in the virtual reality setting, and that participants in the analgesia-expectation group, after the intervention, exhibited significantly higher pain thresholds, and lower pain intensity and unpleasantness ratings than control-expectation participants, independent of the setting. Our findings show that a virtual placebo can elicit placebo analgesia comparable to that of a physical placebo, and that administration of a placebo does not necessitate physical bodily interaction to produce analgesic responses. Perspective: This study demonstrates that a virtual placebo treatment, even when administered to a virtual body, can produce placebo analgesia. These findings indicate that the efficacy of a virtual placebo is comparable to that of a physical placebo, which could pave the way for effective new non-pharmacological approaches for pain management. (C) 2021 by United States Association for the Study of Pain, Inc.