Socially induced placebo analgesia: a comparison of a pre-recorded versus live face-to-face observation

Abstract

Background: Recently, it has been shown that live, face-to-face social observation induces marked placebo analgesia. Despite the phenomenal growth of video sharing platforms, the potential analgesic effects of video-based social observation are largely unknown. This study compared video-based and live social observation induced placebo analgesia and whether there was a similar relationship between analgesic responses and empathy traits for both conditions.

Methods: Here, we compared placebo analgesia in four groups: social observation through a video (SOV group), social observation in person (SOP group), verbal suggestion alone (VS group) and a natural history group (NH group). The SOV and SOP groups underwent a placebo treatment and painful stimuli following respectively a video-based and live observation of a demonstrator showing analgesic effects when the painful stimuli were paired to a green light but not a red light. The VS group received painful stimuli after they had been verbally instructed to expect less pain after the green light. The NH group received painful stimuli, but was told nothing about the meaning of the lights. Individual pain reports and empathy traits were measured.

Results: We found that video-based observation induced substantial placebo analgesic responses that were of similar magnitude to live observation. Notably, the analgesic scores were strongly correlated with empathetic concern in the live observation group but not in the video replay group.

Conclusions: These findings add evidence that placebo analgesia can be induced by social observation and that empathy interacts with these effects in a context-dependent manner.

Fig 1

Visual stimuli sequence and time course for each trial. (A) The red and green boxes represent the pseudorandom order of the 36 visual stimuli (18 red/18 green) presented during the acquisition (SOV and SOP Groups) and the testing phase in all the experimental groups. (B) Each trial began with the presentation of a red/green circle for 5 s, which was immediately followed by the delivery of a painful electric stimulus (delay of 100 ms). Subjects had 1 second to rest and were given 5 s to rate their pain using the VAS. There was an inter-stimulus interval of 15 s.

Fig 2

The graphs show the trial by trial VAS scores reported for stimuli paired with the green light and red light following (A) social observation through a video, (B) live social observation, (C) verbal suggestion alone and (D) a control. For the video based and live social observation groups, stimuli pared with the green light were consistently rated as less painful than those paired with the red light. Verbal suggestions produced no changes in pain modulation in fact there was no difference with the natural history control group.

Fig. 3. Magnitude of pain reduction in each experimental group

The analgesic effects (red minus green differences in VAS scores) in SOV group were not different from those measured in the SOP group but significantly different from those measured in the VS group and the NH group.

Fig. 4

Correlations between EC scores and analgesic responses in the SOV (A), SOP (B), VS (C) and NH (D) groups. Note that there was a positive correlation between EC and pain reduction in the SOP Group only following the live face-to-face observation.