Social laughter triggers endogenous opioid release in humans

Journal article

The size of human social networks significantly exceeds the network that can be maintained by social grooming or touching in other primates. It has been proposed that endogenous opioid release following social laughter would provide a neurochemical pathway supporting long-term relationships in humans (Dunbar, 2012) yet this hypothesis currently lacks direct neurophysiological support. We used positron emission tomography (PET) and μ-opioid-receptor (MOR) specific ligand [11C]carfentanil to quantify laughter-induced endogenous opioid release in 12 healthy males. Before the social laughter scan, the subjects watched with their close friends laughter-inducing comedy clips for 30 min. Before the baseline scan, subjects spent 30 min alone in the testing room. Social laughter increased pleasurable sensations and triggered endogenous opioid release in thalamus, caudate nucleus, and anterior insula. In addition, baseline MOR availability in the cingulate and orbitofrontal cortices was associated with the rate of social laughter. In a behavioral control experiment, pain threshold - a proxy of endogenous opioidergic activation - was elevated significantly more in both male and female volunteers after watching laughter-inducing comedy vs. non-laughter inducing drama in groups. Modulation of the opioidergic activity by social laughter may be an important neurochemical pathway that supports formation, reinforcement, and maintenance of social bonds between humans.SIGNIFICANCE STATEMENTSocial contacts are of prime importance to humans. The size of human social networks significantly exceeds the network that can be maintained by social grooming in other primates. Here we used positron emission tomography to show that endogenous opioid release following social laughter may provide a neurochemical mechanism supporting long-term relationships in humans. Participants were scanned twice; following 30-minute social laughter session, and after spending 30 minutes alone in the testing room (baseline). Endogenous opioid release was stronger following laughter versus baseline scan. Opioid receptor density in the frontal cortex predicted social laughter rates, Modulation of the opioidergic activity by social laughter may be an important neurochemical mechanism reinforcing and maintaining social bonds between humans.

Authors: Manninen, S; Tuominen, L; Dunbar, R; Karjalainen, T; Hirvonen, J

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Society for Neuroscience
• Journal: Journal of Neuroscience
• Volume: 37
• Issue: 25
• Pages: 6125-6131
• Publication date: 2017-06-21
• Acceptance date: 2017-04-10
• DOI: 10.1523/JNEUROSCI.0688-16.2017
• EISSN: 1529-2401
• ISSN: 0270-6474
• Language: English
• Keywords: Journal Article