A Calming Presence

June 1, 2021

Written by: Lisa Wooldridge

If this year has taught us anything, it’s that our social bonds are critical to getting us through stressful situations. The mere act of spending time with friends and family can be immensely stress-relieving, especially after long periods of social distancing. In short, our social networks have proven incredibly valuable for withstanding the major stressors introduced or worsened by the pandemic. Scientists call this well-established phenomenon social buffering

How does social interaction impact stress?

Anything that causes us stress, from public speaking to sprinting away from a charging lion, can trigger a cascade of neurotransmitter and hormone activity throughout the brain and body by activating the hypothalamic-pituitary-adrenal axis, or HPA axis.

Figure 1. Oxytocin mediates social buffering of the stress response. (Black) When our brains detect a threat, it activates the hypothalamic-pituitary-adrenal (HPA) axis to sequentially release a series of neurotransmitters and hormones. These hormones act on many organs throughout the whole body to produce the stress response. (Red) Having a familiar face present during stress causes the hypothalamus to release not just CRF, but also oxytocin. Oxytocin, in turn, counteracts the stress response by decreasing the release of CRF in the hypothalamus; ACTH in the pituitary gland; and corticosteroids in the adrenal gland. 

This activation occurs in four main steps, summarized in Figure 1:

  1. Stress causes the release of a neurotransmitter called corticotrophin-releasing factor (CRF) from the hypothalamus1
  2. CRF travels to the pituitary gland at the base of the brain, where it triggers the release of adrenocorticotropic hormone (ACTH) into the bloodstream. 
  3. ACTH travels to the adrenal glands, where it leads to the release of corticosteroids. 
  4. Corticosteroids circulate and act on your whole body, producing the familiar anxiety-related effects known as the “fight-or-flight” response – sweaty palms, pounding heart, tensed muscles.

Collectively, all of the effects of corticosteroid release mobilize our body’s energy stores to quickly avoid danger. Though the effects of HPA axis activation are useful in response to some types of stress, such as that charging lion, it’s less helpful for others, such as public speaking, and can actually be detrimental. Fortunately, the presence of others during this stress response can ameliorate the effects of HPA axis activation on our bodies and minds. One way interaction can reduce stress is by dampening the amount of corticosteroids available in the blood to activate the fight-or-flight response. During experimentally-induced stress, people who interacted frequently with their social support systems had lower levels of corticosteroids compared to those who didn’t interact with social support2. Humans are not unique in experiencing this benefit – in fact, similar effects are evident in a number of mammals, from rodents to farm animals to primates.  For example, while removing an infant squirrel monkey from its mother usually causes a spike in blood cortisol levels in both the infant and the mother, if a familiar social group is present at the time of separation the cortisol spike is much smaller for both infant and mother3. Likewise, the presence of another rat reduces both the activity of the hypothalamus of rats exposed to a stressful foot shock4 and the corticosteroid spikes in response to an unknown, potentially dangerous new environment5. Scientists have even found similar effects of social support on the brain, behavioral, and corticosteroid response in sheep6 and horses7

 It’s still unclear exactly how social buffering comes about in the brain and body at a chemical level, but it likely has to do with the interplay of the neurotransmitter oxytocin with the HPA axis. Oxytocin is a neurotransmitter critically important for social bonding. It is released during social activities such as breastfeeding and warm touch, and its activity increases affiliative feelings between social partners and amplifies social cues8. Oxytocin is also critical in moderating our stress responses, and direct oxytocin administration has repeatedly been shown to reduce cortisol levels during stressful tasks9

Oxytocin in the brain is primarily produced in the very same region of the hypothalamus that initiates the HPA axis response. Directly blocking oxytocin in the hypothalamus of prairie voles prevents social buffering on anxiety-like behavior and corticosteroid response to stress, suggesting that oxytocin can block corticosteroid spiking by cutting off the HPA axis at its source in the hypothalamus10. However, oxytocin can also act at the other steps of the cascade by blocking the secretion of ACTH and corticosteroids11. In summary, social buffering can come about through socially-induced release of oxytocin, which can then rapidly and thoroughly tamp down stress responses in every part of the pathway. 

Oxytocin’s important role in generating affiliative feelings has allowed us to develop social networks to depend on, helping our species to survive for thousands of years. And although we’ve all experienced social distancing during COVID-19, it’s clear that oxytocin’s role in social buffering has helped many of us survive and thrive.

References:

  1. Hostinar CE, Sullivan RM, Gunnar MR. Psychobiological mechanisms underlying the social buffering of the hypothalamic-pituitary-adrenocortical axis: a review of animal models and human studies across development. Psychol Bull. 2014;140(1):256-282. doi:10.1037/a0032671
  2. Eisenberger NI, Taylor SE, Gable SL, Hilmert CJ, Lieberman MD. Neural pathways link social support to attenuated neuroendocrine stress responses. Neuroimage. 2007;35(4):1601-1612. doi:10.1016/j.neuroimage.2007.01.038 
  3. Coe CL, Mendoza SP, Smotherman WP, Levine S. Mother-infant attachment in the squirrel monkey: adrenal response to separation. Behav Biol. 1978;22(2):256-263. doi:10.1016/s0091-6773(78)92305-2
  4. Takahashi Y, Kiyokawa Y, Kodama Y, Arata S, Takeuchi Y, Mori Y. Olfactory signals mediate social buffering of conditioned fear responses in male rats. Behav Brain Res. 2013;240:46-51. doi:10.1016/j.bbr.2012.11.017
  5. Armario A, Luna G, Balasch J. The effect of conspecifics on corticoadrenal response of rats to a novel environment. Behav Neural Biol. 1983;37(2):332-337. doi:10.1016/s0163-1047(83)91425-5
  6. da Costa AP, Leigh AE, Man MS, Kendrick KM. Face pictures reduce behavioural, autonomic, endocrine and neural indices of stress and fear in sheep. Proc Biol Sci. 2004;271(1552):2077-2084. doi:10.1098/rspb.2004.2831
  7. Ricci-Bonot C, Romero T, Nicol C, Mills D. Social buffering in horses is influenced by context but not by the familiarity and habituation of a companion. Sci Rep. 2021;11(1):8862. Published 2021 Apr 23. doi:10.1038/s41598-021-88319-z
  8. Crockford C, Deschner T, Ziegler TE, Wittig RM. Endogenous peripheral oxytocin measures can give insight into the dynamics of social relationships: a review. Front Behav Neurosci. 2014;8:68. Published 2014 Mar 11. doi:10.3389/fnbeh.2014.00068
  9. Cardoso C, Kingdon D, Ellenbogen MA. A meta-analytic review of the impact of intranasal oxytocin administration on cortisol concentrations during laboratory tasks: moderation by method and mental health. Psychoneuroendocrinology. 2014;49:161-170. doi:10.1016/j.psyneuen.2014.07.014
  10. Smith AS, Wang Z. Hypothalamic oxytocin mediates social buffering of the stress response. Biol Psychiatry. 2014;76(4):281-288. doi:10.1016/j.biopsych.2013.09.017
  11. Kikusui T, Winslow JT, Mori Y. Social buffering: relief from stress and anxiety. Philos Trans R Soc Lond B Biol Sci. 2006;361(1476):2215-2228. doi:10.1098/rstb.2006.1941

Cover photo from Unsplash user Harli Marten.

Summary Figure created with BioRender.com

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