Factors influencing the hypoalgesic effects of virtual reality.

abstractVirtual reality (VR) is a promising intervention for both experimentally induced and clinical pain, but the factors contributing to the efficacy of VR remain relatively unclear, partially because selecting adequate controls in existing VR studies is challenging. Here, we identified and isolated several factors potentially influencing the hypoalgesic effect of VR. In this within-subjects, counterbalanced controlled study, healthy participants received painful heat stimulation under 5 conditions: VR Ocean (immersive ocean environment), Sham VR Ocean (nonimmersive ocean environment), VR Neutral (immersive neutral environment), Imagination (self-imagined ocean environment), and No-intervention. Participants underwent a pain tolerance test under each condition, stopping the heat stimulation when they reached their maximum tolerance. Participants were also divided into a group with information highlighting the VR Ocean as a highly effective intervention, and a control group receiving no such information. Results showed that pain tolerance, expressed in degree Celsius, was significantly higher in the VR Ocean condition compared with all other conditions, despite VR Ocean not attenuating self-reported pain intensity and disengagement from pain. In addition, VR Ocean decreased pain unpleasantness relative to all conditions except Sham VR Ocean. Virtual reality Ocean also improved mood relative to all other conditions and was perceived as the most engaging. Expectations did not affect the results. Taken together, we found that being immersed in an externally generated pleasant environment is key to the hypoalgesic effect of VR. Virtual reality is effective in increasing the level of pain being tolerated and mitigating the subjective affective experience of pain.