The strongest insights into the biological bases of social connection come from animal research, which shows that social bonds rely on the same neurochemicals that support general motivation, among them opioids

Opioids and Social Connection. Tristen K. Inagaki. Current Directions in Psychological Science, https://doi.org/10.1177/0963721417735531

Abstract: Social connection, the pleasurable, subjective experience of feeling close to and bonded with other people, is critical for well-being and continued social bonding. Despite the importance of social connection for many important outcomes, few researchers have experimentally examined how humans connect with those to whom they feel close. The strongest insights into the biological bases of social connection come from animal research, which shows that social bonds rely on the same neurochemicals that support general motivation. One class of neurochemicals, opioids, has received increased attention in recent years with the rise of pharmacological methods to manipulate opioids in humans. This article reviews emerging findings to show that opioids affect social feelings, behaviors, and perceptions in both positive and negative social experiences and concludes with the implications of such findings. Future work should consider the subjective feelings of social connection felt during interactions with close social contacts in order to further the understanding of social connection.

Keywords: social affiliation, social bonding, attachment, social reward, endogenous opioids