Loneliness isn't just a social problem — it's a physical problem as well, as scientific research over the past decade has revealed in spades. Research into the topic has found links between social isolation and a variety of physical and mental health conditions, including heart disease, high blood pressure, depression and anxiety. Knowing this, some social critics are asking a once-unthinkable question: should social contact be treated as a basic need, on par with food, water, sleep and shelter?
Research suggests that the answer is yes, in part because we now have a better understanding of how the human body responds to loneliness — and, in contrast, adversely reacts to a lack of social connection. According to a new study published by scientists in Psychological Science, the flagship journal of the Association for Psychological Science, the same part of the brain that is triggered when a person is hungry is activated when a person is lonely, too.
In the study, scientists looked into the effects of social isolation in two different contexts: in the lab, and at home during COVID-19 lockdown. The study involved 30 female volunteers who visited their lab on three occasions, spending eight straight hours either without food, without social contact, or with both food and social contact. Throughout the experiment, the women indicated when they were stressed, experiencing mood changes or fatigued. Scientists recorded their physiological stress responses, such as heart rate and cortisol — and found they were similar to when they were hungry for food.
"In the lab study, we found striking similarities between social isolation and food deprivation," said authors Ana Stijovic and Paul Forbes in a joint press statement. "Both states induced lowered energy and heightened fatigue, which is surprising given that food deprivation literally makes us lose energy, while social isolation would not."
"In the lab study, we found striking similarities between social isolation and food deprivation."
The researchers suggest that the lowered energy experienced by a lack of social contact could be the beginning of long-term detrimental effects of social isolation. The researchers compared their findings to a similar study conducted during the pandemic to validate their findings, which suggest a "social homeostasis" occurs in the brain when it's socially isolated for too long.
"It is well-known that long-term loneliness and fatigue are related, but we know little about the immediate mechanisms that underlie this link," Silani said. "The fact that we see this effect even after a short period of social isolation suggests that low energy could be a 'social homeostatic' adaptive response, which on the long run can become maladaptive."
The findings are aligned with previous research that has found links between loneliness and hunger. In 2020, researchers at the Massachusetts Institute of Technology found that both loneliness and hunger share signals in the brain that govern basic reward and motivation impulses, also suggesting that our need to connect with others is as essential as the need to eat.
"Despite the fact that isolation lasted only 10 h[ours], and the participants knew exactly when it would end, participants reported more loneliness and social craving at the end of the day than they did at the beginning," the MIT researchers concluded. "For people who are highly socially connected, a day of social isolation is a large deviation from typical rates of social interaction."
Notably, the researchers stated that rest and isolation — when chosen — is good for us. Still, they emphasized an open question is how much social interaction does that brain need in order to not feel "hungry" is an open-ended question for researchers to answer.
"For people who are highly socially connected, a day of social isolation is a large deviation from typical rates of social interaction."
Yet in terms of its capacity to become a social problem, loneliness is much harder to measure quantitatively than, say, other social problems like hunger or medical care or housing. Indeed, there is a lot of confusion around the source of loneliness; or the lack of social contact such that loneliness reaches a point where a person's physical health is affected, especially if the lonely are physically around others all of the time. Of course, one cannot completely escape loneliness, as it is a natural part of the human experience; or "la condition humaine," as a French existentialist might say.
Yet researchers are working on quantitative measurements, such as the UCLA loneliness scale — according to which there are unhealthy tipping points.
"Loneliness has more to do with a person's perception of whether they're in enough meaningful relationships," Cat Moore, the Director of Belonging at the University of Southern California, previously told Salon. "Psychologists say there are thresholds that vary for each person and they aren't related to the number of friends and followers we have on Facebook or the people we recognize when we go out and say "hi" to [them]."
Moore said it has to do more with relationships reaching a certain level, and when that layer of a relationship isn't met, that loneliness can manifest into other mental and physical health problems.
Either way, when feeling lonely, Moore compared it to a feeling of hunger as well.
"Loneliness is indicating to you that a social need isn't being met, like when you're hungry, your stomach tells you that you need food," Moore said.
