As the world faces growing challenges related to loneliness, chronic pain and opioid misuse, there is a pressing need to better understand the neurobiological systems that link these issues. Research in animals long pointed to the brain’s endogenous opioid system as a key player in regulating pain, stress, reward, and social bonding. But how are these findings relevant for understanding human social behaviour and how social relationships promote resilient outcomes in face of stress and adversity?
This doctoral thesis explores the role of the opioid system in human sociality, with a particular focus on how it shapes emotional responses to social interaction and support. Through on two narrative reviews, a systematic review and meta-analysis, and three experimental studies, the thesis finds that while opioid signalling may subtly modulate social emotions and behaviour, it does not appear to be essential for the benefits of social support. These findings challenge influential neurobiological theories that position opioids as primary drivers of social motivation and attachment.
The work points to a need for more nuanced models of how supportive relationships promote resilient outcomes – models that account for the complex interplay between multiple brain systems and contexts. Importantly, the intact benefits of social support observed during opioid blockade suggest that individuals with disrupted opioid system function – such as those with substance use disorders, chronic pain or depression – are likely still able to build resilience from supportive social relationships