Full title of the project: "Opioid-blunted cortisol response to stress is associated with increased negative mood and wanting of social reward".

Team: Claudia Massaccesi and Giorgia Silani (Clinical Social Neuroscience unit) in cooperation with Urs M. Nater and Claus Lamm (all University of Vienna), Matthaeus Willeit (Medical University of Vienna), Boris B. Quednow and Daniel Mueller (University of Zurich).

Institute/Department: Clinical Social Neuroscience Unit, Department of Clinical and Health Psychology.

Goal of the project: The main goal is to investigate the effects of morphine administration, a selective μ-opioid receptor agonist, on psychological and physiological responses to stress and stress-induced wanting and liking of social rewards, delivered in the form of gentle caresses.

Why is this important and useful? A better understanding of the effects of opioids on stress resilience and social behavior is fundamental, as opioid drugs are widely consumed.  Additionally, understanding the neurochemistry of social motivation can help improving treatments of conditions characterized by social impairments..

Abstract: Animal research suggests a central role of the μ-opioid receptor system in regulating affiliative behaviors and in mediating the stress-buffering function of social contact. However, the neurochemistry of stress-induced contact seeking in humans is still poorly understood. In a randomized, double-blind, between-subjects design, healthy female volunteers (N = 80) received either 10 mg of the µ-opioid agonist morphine, or a placebo. Following a standardized psychosocial stress induction, participants engaged in a social reward task, in which the motivation to obtain skin-to-skin social touch and the hedonic reactions elicited by such touch were assessed. Morphine prevented the increase of salivary cortisol typically observed following acute stress exposure. Notably, this altered physiological responsivity was associated with increased negative affect in response to psychosocial stress, and enhanced subjective wanting of social contact. These findings provide novel evidence on the effect of opioids administration on reactions to psychosocial stress and point to a state-dependent regulation of social motivation.

Explanation - easy to understand: Participants administered morphine had less cortisol (a hormone which usually increases with stress) in their saliva. They also reacted more negatively to stress and had a higher desire for pleasurable physical contact (caresses to the forearm). These results suggest that opioids may decrease our ability to cope with stressful events. And that after acute stressful experiences, physical contact with others may have a calming effect.

Article in "Nature Neuropsychopharmacology": https://www.nature.com/articles/s41386-022-01283-8