Naltrexone alters responses to social and physical warmth: implications for social bonding.

Tristen K Inagaki,Carmen Andreescu,Laura I Hazlett

doi:10.1093/scan/nsz026

Abstract

Socially warm experiences, when one feels connected to others, have been linked with physical warmth. Opioids, hypothesized to support social bonding with close others and, separately, physical warmth, may underlie both experiences. In order to test this hypothesis, 80 participants were randomly assigned to the opioid antagonist, naltrexone or placebo before neural and emotional responses to social and physical warmth were collected. Social and physical warmth led to similar increases in ventral striatum (VS) and middle-insula (MI) activity. Further, feelings of social connection were positively related to neural activity to social warmth. However, naltrexone (vs placebo) disrupted these effects by (i) reducing VS and MI activity to social and physical warmth, (ii) erasing the subjective experience–brain association to social warmth and (iii) disrupting the neural overlap between social and physical warmth. Results provide additional support for the theory that social and physical warmth share neurobiological, opioid receptor-dependent mechanisms and suggest multiple routes by which social connections may be maintained.

Highlights

Close social connections and the feelings that come from being connected to other individuals are of utmost importance
How do we feel close and connected to our loved ones? The present study is the first to show that the opioid antagonist, naltrexone, reduces ventral striatum (VS) and MI activity to both social and physical warmth and erases the neural overlap between the two experiences
The brain opioid theory of social attachment suggests that blocking opioid activity would subsequently alter social connection (Panksepp et al, 1980a; Panksepp, 1998)

Summary

Introduction

Close social connections and the feelings that come from being connected to other individuals are of utmost importance. We examine in the current study the causal role of opioids in feelings of social connection, neural activity to an experience of social connection and the potential overlapping contribution of physical warmth to social connection. Due to the importance of social connection for well-being, basic homeostatic mechanisms that maintain individuals at an optimal level of functioning may be involved in the maintenance of social bonds (Panksepp et al, 1980a; Panksepp, 1998). According to the brain opioid theory of social attachment, opioids contribute to emotional responding within close relationships and to the behavior or feelings that might promote further bonding (Panksepp et al, 1980a; Machin and Dunbar, 2011; Inagaki, 2018). Evidence for the theory comes primarily from animal research, which has shown that pharmacologic manipulations of the

Objectives

Methods

Results

Conclusion