Lack of social interaction is associated with an increased risk of cardiovascular disease, dementia, and more. Researchers are exploring how the brain mediates these effects.
In 2010, Teresa Chaclos was diagnosed with chronic lymphocytic leukemia, the first of a series of diseases she has had to face in recent years. She has always been an independent person, living alone as a Family Law Coordinator in the Washington, D.C. court system. But when the disease hit, her independence turned into loneliness.
Loneliness, in turn, exacerbated Chaclos's physical condition. "In less than a week, I lost 15 pounds because I didn't want to eat," she said. "I was in so much pain that I just wanted to get out of bed. Luckily, a colleague persuaded her to seek help from a friend, and her mood began to improve. "It's a great feeling to know that other people are willing to show up," she said.
Many people can't easily get out of the predicament of loneliness. When acute loneliness becomes chronic, its health effects ripple throughout the body. According to a report by U.S. Physician General Vivek Murthy, chronic loneliness is just as harmful as obesity, lack of exercise, and smoking. Depression, dementia, cardiovascular disease, and even early death have been linked to this condition. According to a 2023 poll conducted by social media firm Meta, polling firm Gallup, and a group of academic advisors, about a quarter of adults worldwide feel very or fairly alone. That same year, the World Health Organization launched a campaign to tackle loneliness, calling it an "urgent health threat".
How does loneliness damage the brain?
But why does loneliness lead to health problems? In recent years, scientists have begun to unravel the neural mechanisms that cause the human body to collapse when social needs cannot be met. Nathan Sprenger, a cognitive neuroscientist at McGill University in Montreal, Canada, said the field "seems to be expanding rapidly". Although it's not entirely clear, early results suggest that loneliness may alter many aspects of the brain, from brain volume to connections between neurons.
Loneliness is an elusive concept. It is different from social isolation, which is when a person has few meaningful social relationships, even though "they are two sides of the same coin," says Andrew Somerald, a geriatric psychiatrist at University College London. On the contrary, loneliness is a subjective experience in which a person is dissatisfied with their social relationships.
The list of health conditions associated with loneliness is long and sobering. Some of these are intuitive, for example, people who feel lonely tend to be depressed and sometimes even suicidal. Other connections are even more surprising. For example, lonely people are at greater risk of developing high blood pressure and immune system dysfunction than people who don't feel lonely. There is also a striking link between loneliness and dementia, with one study reporting that people who felt lonely were 1.64 times more likely to develop the neurodegenerative disease than those who did not.
A number of physiological effects, including the ability to sleep, increased levels of stress hormones, and increased susceptibility to infections, may link loneliness to health problems. But Livia Tomova, a cognitive neuroscientist at Cardiff University, warns that the way these factors interact makes it difficult to separate the effects of loneliness from the causes. Do people's brains start to function differently when they become lonely, or do some people have differences in their brains that make them feel lonely easily? "We don't really know which one is true," she said.
Social class and loneliness
Whatever the reason, loneliness seems to have the greatest impact on people in vulnerable groups. According to a 2021 survey by Cigna Group, a U.S. health insurance company, in the U.S., black and Hispanic adults, as well as those earning less than $50,000 a year, have loneliness rates at least 10 percentage points higher than other demographic groups. Ashwin Cottwal, a geriatrician and palliative care physician at the University of California, San Francisco, says this is not surprising because "loneliness is, by definition, an emotional pain that makes us want to fit into our social environment." Adaptation is even more difficult if economic resources are lacking.
The pandemic may have exacerbated loneliness as people were forced to isolate for months or years, even though "the data is still coming in," Cottwal said. Older people have long been considered to be the group most affected by loneliness, and in fact, many of the older people Koutwal came into contact with did face loneliness. But data from the Cigna Group suggests that loneliness is actually worst among young people – 79% of people between the ages of 18 and 24 report feeling lonely, compared to 41% of those aged 66 and over.
The vicious cycle of loneliness
Researchers also found some differences in looking for neurological features of loneliness that may help explain some of the correlations between loneliness and dementia. Previous studies have shown that there are changes in the connections between brain regions in people who feel lonely. A 2020 study looked at the role of the default network in the brain, which is when a person is not engaged in a specific task and turns their attention inward. The study was aimed at older adults who reported feeling lonely.
Previous research has shown that there is a high degree of neural crosstalk between the default network and other networks related to vision, attention, and executive control among young people who feel lonely. Probably because they are highly wary of social cues. But his team found the opposite in brain scans of people aged 40 to 69 at the UK Biobank. Solitude weakens the connection between the default network and the vision system, and enhances the connection inside the default network.
Sprenger said this may be because older adults compensate for their loneliness by recalling past social experiences. In doing so, they have strengthened the default network.
The default network is one of many networks in the brain that can be compromised during Alzheimer's disease. Sprunger and his colleagues are investigating whether strong default networks can actually be linked to neurodegenerative diseases – and if so, why? The idea is far from being proven, but it's a plausible explanation and "an interesting hypothesis," says Anastasia Benedik, a cognitive neuroscientist at the Central Institute of Mental Health in Mannheim, Germany.
The study "laid the groundwork for us to be able to test some of our hypotheses more empirically," says Mwiramwe-Tssilobo, who is also involved in research linking default networks to loneliness.
Find a solution
Some solutions to loneliness are not surprising. Increasing access to social activities, such as letting people live in communities with common areas, can help, Somerald said. Some researchers are also finding ways to directly tap into the neural mechanisms behind loneliness, for example through exercise.
Benedik and her colleagues found that walking 4-5 kilometers could completely reverse the depression associated with loneliness in some people. In addition, people with high internet connectivity by default — the same area that Splenger studied, which was also found to be affected by depression — were among those who benefited the most from exercise.
One possible explanation for this observation is that people with depression are "lost in thought" – a behavior that relies heavily on the default network. Benedic says that exercise can be done by interrupting the ???? associated with self-reflection The process and the transfer of its activity to the areas associated with physical activity force them to use other parts of the brain – freeing them from the cycle of negative thoughts.
Exercise is also a great excuse to socialize. Today, Chaclos is retired, but she now leads the Boston chapter of a U.S. program called Walking with Doctors, in which doctors invite community members to walk with them. About 14 people chatted and strolled around the Prudentence Center Mall in Boston, Massachusetts, where they could escape the New England winter climate, during the group's February walk. Chaclos said the activity "just lifted one's mood." "Even if you're still going to go home and be alone, you don't feel completely alone anymore. ”
