Loneliness has become one of the most significant public health issues, prompting the surgeon general to issue an advisory calling it and social isolation an “epidemic” back in 2024. Perhaps one of the biggest misconceptions is that loneliness only causes sadness. However, research links it to other issues, including serious health risks and diseases.
The Dangers of Loneliness
The Centers for Disease Control and Prevention (CDC) defines loneliness as the feeling of being alone or disconnected, while social isolation refers to actually having few social relationships or little contact with others. The two don't always happen together. You can feel lonely in a crowd or feel perfectly content living alone.
According to the CDC, about one in three US adults reports feeling lonely, while around one in four say they don’t have any social and emotional support. Loneliness and social isolation increase the risk of various diseases, including heart disease, stroke, type 2 diabetes, depression, anxiety, dementia, and premature death.
The Surgeon General’s Advisory showed that poor social relationships increased the risk of heart disease by 29% and stroke by 32%. Furthermore, among older adults, who are more susceptible to loneliness, there is about a 50% greater risk of developing dementia.
Researchers believe prolonged loneliness keeps the body’s stress response activated, which increases inflammation, raises blood pressure, disrupts sleep, and weakens the immune system.
Humans Need Social Connections
Where I'll be, I'll be so lonely, baby
Well, I'm so lonely
I'll be so lonely, I could die
Elvis Presley may have been singing about romantic heartbreak in "Heartbreak Hotel," but those famous lyrics speak to a serious health problem that continues to grow in today’s society. At one time or another, nearly everyone experiences loneliness, but it’s the extent of the isolation that causes the issues.
Long ago, humans survived by living in groups. If someone became separated from the group, their chances of survival diminished. People depended on each other for everything from protection to hunting to raising children. Dr. Stephen Braren wrote in an article for Social Creatures, explaining that loneliness is an evolutionary warning system. Just as hunger signals the need for food and thirst signals the need for water, loneliness signals that a person’s need for social connection is not being met.
“Some of the strongest evidence for the idea that the need for social connection has evolved in humans is the fact that humans have unusually large brains,” Braren said. “Across animals, brain size is highly correlated with body size. Large animals like whales have large brains whereas small animals like mice have small brains. But humans have incredibly large brains relative to our body size.”
Why does this matter? In the 1990s, anthropologist Robin Dunbar suggested that our brains grew because humans needed to manage increasingly complex social lives. As people lived in larger groups, they had to remember more relationships, understand social rules, and work together. Dunbar found that animals living in larger groups generally have bigger neocortexes, or the outer part of the brain involved in thinking and social behavior. In other words, our brains grew bigger because connecting with other people became essential for survival. “Basically, we evolved big brains in order to connect,” Braren said.
More recently, scientists have used brain scans to study how we handle social interactions. They found that the brain uses different networks for social and non-social activities. As soon as we stop doing a particular task, the brain quickly switches back to thinking about people and relationships. In other words, we naturally default to social thinking.
Neuroscientist Matthew Lieberman wrote an article titled “Why We Are Wired to Connect,” published by Scientific American, explaining: “Evolution has placed a bet that the best thing for our brain to do in any spare moment is to get ready to see the world socially. I think that makes a major statement about the extent to which we are built to be social creatures.”
Braren referenced how a group of researchers studied the brain activity of people after they spent ten hours alone and, on a separate day, ten hours without food. After being isolated, participants showed increased brain activity when they looked at pictures of their favorite social activities, and they reported feeling lonely and wanting social connection. After fasting, the same part of the brain became more active when they looked at pictures of their favorite foods, matching their feelings of hunger. The findings suggest that loneliness creates a craving for human connection, much like hunger creates a craving for food.
From the beginning, our survival depended on one another. Families lived close together, neighbors knew one another, and daily life naturally created opportunities for interaction. Thousands of years later, our technology has changed dramatically, but our biology apparently hasn't. Modern life has made it easier than ever to communicate, yet somehow we don’t find the opportunity for face-to-face connections. We can text several people in a day, interact with hundreds on social media, and still feel lonely.
