The opioid system and the social brain: implications for depression and suicide.

In the past decade, considerable attention has been drawn to social interactions and behaviors as sources of pleasurable (social reward) and painful (social pain) emotional states. While the role of the opioid system in the regulation of reward and pain processes has long been recognized, it has more recently been investigated and characterized in the specific context of social experiences across several mammalian species. Accordingly, the present narrative review provides a comprehensive summary of studies detailing how the opioid system controls social reward and social pain. From a translational and pathophysiological perspective, we further discuss how opioid-dependent regulation of social behaviors may contribute to depressive illness and suicidal behaviors, and ultimately provide innovative therapeutic opportunities.