Opioid-blunted cortisol response to stress is associated to increased negative mood and wanting of social reward

Abstract

Animal research suggests a central role of the mu-opioid receptor (MOR) system in mediating contact seeking and the stress-buffering function of social touch. However, the human neurochemistry of social motivation in aversive situations is still poorly understood. In a randomized, double-blind, between-subject design, healthy female volunteers (N = 80) received either 10 mg of the mu-opioid agonist morphine sulfate or a placebo. Following psychosocial stress induction, participants engaged in a social reward task, in which the motivation (subjective ratings of wanting and physical effort) to obtain skin-to-skin social touch and the hedonic reactions (subjective ratings of liking and facial electromyography) elicited by it were assessed. Morphine administration prevented the increase of salivary cortisol, usually observed in response to acute stress exposure. The dampened physiological reaction to the psychosocial stress was associated with increased negative mood and subsequent higher subjective wanting of the most pleasurable touch. Furthermore, participants administered with morphine displayed greater activity of the corrugator muscle during reward anticipation, possibly tracking enhanced attention toward the social stimuli. Overall, the results provide novel evidence on the effect of exogenous opioids administration on the reactions to psychosocial stress and point to a state-dependent regulation of social motivation.