Blocking mu-opioid receptors inhibits social bonding in rituals. S. J. Charles, M. Farias, V. van Mulukom, A. Saraswati, S. Dein, F. Watts and R. I. M. Dunbar. , October 14 2020. https://doi.org/10.1098/rsbl.2020.0485
Rolf Degen's take: https://twitter.com/DegenRolf/status/1316377518480535552
Abstract: Religious rituals are universal human practices that play a seminal role in community bonding. In two experiments, we tested the role of mu-opioids as the active factor fostering social bonding. We used a mu-opioid blocker (naltrexone) in two double-blind studies of rituals from different religious traditions. We found the same effect across both studies, with naltrexone leading to significantly lower social bonding compared with placebo. These studies suggest that mu-opioids play a significant role in experiences of social bonding within ritual contexts.
4. General discussion
Previous work on the role of opioids on social bonding has been conducted either via proxy measures [18,40,41] or via daily self-reporting of social bonding after it has taken place [24]. Here, we sought to understand the role of opioids on social bonding in an ecologically valid setting [2,18,42]. We have demonstrated that mu-opioids play a key role in the social bonding experience during ritual by showing that naltrexone, compared with placebo, lowers feelings of bonding. These results were consistent and individually significant across the two studies. This is the first set of studies to demonstrate the causal role of mu-opioids on bonding during a ritual, and we do so in both a laboratory and a field setting.
It has often been suggested that one of the primary functions of religion is to promote social bonding and thus enhance group solidarity (e.g. [43]). These results extend previous work by providing evidence for a mechanism for how group solidarity might be promoted. In so doing, the results support the brain-opioid theory of social attachment [2,44], which argues that the endogenous opioid system is a major neuroendocrine system underlying social bonding.
Although the sample size of study 1 is small, it adds significantly to study 2 by showing that the results hold across two different cultures and ritual types, thereby providing strong ecological validity [39]. Although it is possible that other neurochemicals such as oxytocin [45,46] and dopamine [47] might also play a role in the social bonding experience, studies of the receptor genetics for these other neurochemicals suggest that these play a more specialized and much less prominent role compared with β-endorphins [1,4]. Still, future research could seek to rule out the role of other such neurochemicals that have been proposed to play a role in bonding in further double-blind studies to determine which neurochemicals are necessary and/or sufficient for social bonding to occur. Study 1 (but not study 2) suffered from the limitation that it recruited very few males, and it would be desirable to increase the gender representation in future studies. It should also be noted that naltrexone may also block the kappa-opioid receptors [20,21], which have a particular affinity with dynorphins. Although this makes it difficult to be absolutely certain that the primary target is the mu-receptors, primate social bonding has been explicitly identified in previous studies with the β-endorphins [48], which have a particular affinity for the mu-receptors.
In summary, we provide the first placebo-controlled, double-blind studies to examine the pharmacological basis for the role of religious rituals in social bonding. These studies provide a prima facie case on the neurochemical mechanisms underlying ritual social bonding.
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