For years researchers studied prairie voles to better understand the neural and endocrine mechanisms that influence these behaviors. With time, some eventually came to ask what would happen if you took one of these highly social rodents and housed it in isolation.
What behavioral and physiological effects would this have on a prairie vole? How much could be extrapolated from such experiments with regard to humans? What would the results mean for the friendless child? The middle-aged adult struggling to connect in a world where disconnection is the norm? The widow or widower? The forgotten senior?
In humans, we tend to see similar patterns, although interpreting data from people on the health consequences of social isolation tends to be a bit trickier than interpreting animal data. Isolating people for extended periods has generally been considered unethical for obvious reasons thus precluding proper experiments. Also, for humans, there is an important distinction between objective states of social isolation and subjective experiences of loneliness.
The reason we see these pathologies in isolated prairie voles and lonely humans is in some ways simple, although simultaneously complex. For social mammals (and probably other social animals), social isolation is likely experienced as a threat to survival at a neurophysiological level. This leads to a stress response. Hence, if sustained, prolonged social isolation can be considered a form of chronic stress, which can take a greater toll on an individual than if the threat or the stressor lasted only a short duration.
In response to perceived threats or various stressors, the hypothalamus releases corticotropin-releasing hormone (CRH), which stimulates the release of adrenocorticotropic hormone (ACTH) by the pituitary gland. ACTH then acts on the adrenal glands, which, in turn, release a glucocorticoid hormone: cortisol in humans, corticosterone in prairie voles.
This glucocorticoid hormone then influences numerous physiological functions, including those related to an organism’s metabolism and cardiovascular system. Glucocorticoid hormones also provide an important negative feedback mechanism to suppress the release of CRH and ACTCH by acting on the hippocampus, hypothalamus, and pituitary.
With regard to the sympathetic nervous system, this system also works, in part, by acting on the adrenal glands, stimulating the release of epinephrine and ultimately yielding physiological effects generally associated with the fight-or-flight response such as elevated heart rate and increased blood glucose levels. In healthy individuals, the activity of the sympathetic nervous system is in some ways kept in check by the related parasympathetic nervous system.
In other words, oxytocin can counteract or rein in dysregulated stress response systems. However, for an isolated or lonely individual, experiences of an additional stressor beyond their isolation presumably will put them in the position of not only experiencing an additional source of stress, but also of being less capable of coping with it than they would have been if they were not alone.
According to some models of disease, the effects of multiple stressors can be cumulative, with increased stressors leading to increased risk of conditions ranging from depression to cancer. Presumably, experiencing them in isolation does not help one’s chances of staving off those ills.
Academically, scientifically, and medically, understanding this has raised all sorts of interesting questions regarding how an individual’s lifestyle, job, or living situation may influence their overall health or risk for a particular disease. It has raised questions regarding what the presence of strong social connections in one’s life may mean for their risk of certain fates. It has raised questions of what the absence of such social connections may mean for the friendless child. The middle-aged adult struggling to connect in a world where disconnection is the norm. The widow or widower. The forgotten senior.
Yet, given all that took place during the Pandemic Era, understanding the relationship between stress, loneliness, and social connection also raises questions somewhat unique to this point in history.
What were the cumulative health effects of encouraging, coercing, and forcing large populations into states of prolonged social isolation while simultaneously instilling in them intense fear and inflicting upon them economic uncertainty and hardship? What will the long-term effects of this be? And how could our public health experts not have considered that doing this to a social mammal might have been bad for their health?
Given their failure in this regard, one can only hope that before the next pandemic, some of our public health experts may get to know a prairie vole.