The effects of different types of pain modulation on social emotions and behaviour - a systematic literature review

Changes to one’s pain processing system via external or cognitive influences may influence how we perceive the world around us and interact with other people. To investigate the causal effects of different types of (psycho)pharmacological pain modulation on social emotions and behaviour, we conducted a pre-registered PRISMA-guided, systematic literature review. Our main aim was to investigate how interfering with the perception of pain in oneself through (psycho)pharmacological manipulations affects our abilities to perceive, process and react to positive and negative emotions (including pain) in other individuals. We included and synthesized 50 out of 2060 screened studies. Included studies investigated the effects of opioids and opioid antagonists, acetaminophen, capsaicin, cannabinoids, ketamine, alcohol, placebo analgesia and hypnotic analgesia. Overall risk of bias was low in 23, medium in 12 and high in 14 studies, while only 24% of studies checked whether the manipulation reduced first-hand pain (which it did in all of these). In summary, studies report inconsistent results, with findings generally showing small effects in both directions, i.e., an increase or decrease of social emotions or abilities. The strongest and most consistent effect was observed for placebo analgesia decreasing empathy for pain. These results can be attributed to study heterogeneity, pharmacological effect and mode of action, as well as dosage differences. This review thus shows that we are far away from understanding the intricacies of different (psycho)pharmacological pain manipulations and their effects on social emotions and behaviour. To advance as a field and better understand the mechanisms of this interplay, we need well-powered studies, large-scale, systematic replications and meta-analyses.