Loneliness and the brain

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Scientists have studied social interactions to understand the deleterious effects of social isolation, but research shows loneliness affects the structure of the brain. Studies of the brain could pave the way to future treatments of diseases stemming from loneliness.

Written by Brett J. Weiss

June 20, 2020

According to the US Census Bureau, approximately 31 million Americans lived alone in 2010. By 2050, the US Census Bureau predicts between 43.2 and 57 million Americans will live alone. Perceived social isolation also continues to increase, with recent reports indicating loneliness affects more than 40% of the older adult population in the US.

With an aging population in industrialized countries and rising perceived social isolation, integrating human and animal studies of isolation to determine underlying physiological mechanisms and treatment options gains relevance worldwide.

A better understanding of the neurophysiology of loneliness for better treatments may help to confront findings of loneliness increasing morbidity, the likelihood of disease, and mortality, the likelihood of death. Especially surprising, social isolation contributes to morbidity and mortality as strongly as smoking, obesity, sedentary lifestyle, and high blood pressure.

To explain the effects of social isolation on increased morbidity and mortality, scientists came up with the social control hypothesis, which says the influence of and obligations to social network members tends to discourage poor health decisions. When people integrate into cohesive social networks, this increases the likelihood they will engage in good health behaviors, such as exercise.

The focus on concrete social relationships, such as marriage or contact with friends, led to the impression that neuroscience and animal studies were irrelevant in determining how social isolation increases morbidity and mortality. At the same time, the brain constitutes the primary organ mediating social relationships in not only humans but other animal species. The brain not only responds to stimuli but also categorizes, abstracts, and evaluates stimuli in the context of current goals and prior experiences.

This begs the question that if the brain plays such an essential role in forming social connections and performing social processes, does a perception of social isolation impact brain structures and processes? Research indicates associations between loneliness and density of brain tissue, gray matter. Specific regions of the brain activate to social stimuli but not to nonsocial stimuli, also.

The research on the effects of perceived social isolation and loneliness in humans remains limited. Neuroscientists have thus turned to the study of animals, including rodents, to answer questions of how perceived social isolation affects brain structures with hopes of translating the research to humans, eventually. The research in adult rodents shows isolation-induced differences in fatty tissue, myelination, toward the front of the brain, the prefrontal cortex. Further research on rodents indicates these differences relate to behaviors such as social withdrawal, aggression, anxiety, and depressive behavior. These behaviors can also characterize lonely individuals, which provides a basis for translating some of these findings to research on loneliness in humans.

“Just a kind of a nightmare that your mind manufactured for you. You see we can feed the stomach with concentrates. We can supply microfilm for reading, recreation, even movies of a sort. We can pump oxygen in and waste material out, but there’s one thing we can’t stimulate. That’s a very basic need. Man’s hunger for companionship. The barrier of loneliness. That’s one thing we haven’t licked yet,” as related from the Serling & Stevens 1959 episode of the Twilight Zone. Perhaps studies of the brain will shed more light on this all-too prevalent quandary of the human condition.

Story source

  1. Cacioppo S, Capitanio JP, Cacioppo JT. Toward a neurology of loneliness. Psychol Bull. 2014;140(6):1464-1504. doi:10.1037/a0037618

Journal references

  1. Cacioppo JT, Norris CJ, Decety J, Monteleone G, Nusbaum H. In the eye of the beholder: individual differences in perceived social isolation predict regional brain activation to social stimuli. J Cogn Neurosci. 2009;21(1):83-92. doi:10.1162/jocn.2009.21007
  2. House JS, Landis KR, Umberson D. Social relationships and health. Science. 1988;241(4865):540-545. doi:10.1126/science.3399889
  3. Kanai R, Bahrami B, Duchaine B, Janik A, Banissy MJ, Rees G. Brain structure links loneliness to social perception. Curr Biol. 2012;22(20):1975-1979. doi:10.1016/j.cub.2012.08.045
  4. Perissinotto CM, Stijacic Cenzer I, Covinsky KE. Loneliness in older persons: a predictor of functional decline and death. Arch Intern Med. 2012;172(14):1078-1083. doi:10.1001/archinternmed.2012.1993

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