Why Lonely People Get Sick More Often

We all know about heartache. For some, feeling alone can be physically painful. And a strong body of recent research has established that it's not just in our minds. Chronic social isolation is linked to heart disease—it stresses the entire cardiovascular system—and can also hurt our ability to fend off colds and other viruses. But the cause of those connections has been unclear. Is it that lonely people have fewer social resources, meaning no one to rely on when they fall ill, or can the sensation of loneliness change their biology?

A study out this week suggests that it's the latter: loneliness actually changes how the body functions at a molecular level. The research links feelings of social isolation to an alteration in the activity of specific genes—ones that put lonely people at higher risk for serious disease. And the study, published in the current issue of Genome Biology, also points to the startling fact that it is the perception of loneliness that triggers the adverse health conditions, independent of how much social interaction an individual actually has. Even someone with hundreds of "friends" on Facebook or at the office might think of herself as a lonely person.

So how can feeling lonely translate into poor health? Researchers believe that chronic social isolation sets off a biological chain reaction that causes normal immune responses to malfunction. It starts with the lonely individual's outlook on the world, in which, typically, other people are perceived as threatening. This makes social interactions—going to a party, for example—more stressful. "Chronically lonely people have a subjective theory of the world that says that people can't be trusted," says Steven Cole, assistant professor at the UCLA School of Medicine and the study's lead author. "It's not that they're hostile; they just perceive the world as somewhat more threatening."

That perception cues the body to produce a stress hormone called cortisol. In a healthy immune system, cortisol tells a group of genes to shut down the body's inflammatory response. But in a person who's chronically stressed or anxious due to loneliness, that process is altered. Here's how it works: for most people a low level of inflammation is normal; it means the body is performing general maintenance and responding to minor, sometimes unnoticeable threats. However, high levels of inflammation are worrisome. In autoimmune diseases, for example, the body attacks its own tissues and causes an increase in inflammation. Inflammation is also linked to a number of serious health risks, including cancer. Cole and his colleagues found that lonely individuals consistently had higher levels of inflammation even though they were producing a slightly higher level of cortisol—the hormone that should be shutting down the inflammatory response. The receptors, Cole says, were not responding properly, probably because they were receiving a constant stream of cortisol. "If you send a signal to a receptor all day long it will stop listening," says Cole. "Essentially, it's like the immune system saying that cortisol is crying wolf."

That accounts for the higher levels of inflammation the researchers observed in chronically lonely individuals. But they also found other faulty immune responses: lonely people produced fewer antibodies, which the body uses to tag pathogens, like bacteria and viruses. They also had a lower antiviral response; a group of genes involved in fighting viruses were not expressing themselves as much. "The risky parts of the immune system are going too hard, and the health-protective parts are not going hard enough," says Cole.

Interestingly, what causes that imbalance isn't how many pals an individual has or the number of social interactions. Rather, the loneliness that leads to these adverse health conditions is tied to how individuals perceive their social situations. "Loneliness is inherently subjective," says Steven Asher, a psychology professor at Duke University who was not affiliated with the study. Asher has spent decades studying friendship and loneliness and says that an individual's level of social interaction does not necessarily say anything about his or her loneliness.

"You can measure how many friends they have, and whether they provide support, but the only way you can know if somebody is lonely is to ask them," says Asher. He has observed individuals with many friends who will report being lonely and, on the opposite side, those with few friends who do not. And, like Cole, Asher has found that lonely individuals tend to have a distinctly different outlook on social interactions. "We find that people who are lonely are more socially anxious," Asher says. "They're definitely feeling more stress and more anxiety."

So what should lonely guys and gals do if they're worried about their health? Harvard Medical School experts suggest talk therapy. For those who want to tackle the loneliness head on, helping others can be a fantastic way to make essential social connections. Tutoring in a subject you know at a local school or any kind of volunteer work can provide all-around benefits and bring you close to people of like mind. Even just one new but meaningful contact can make all the difference. And to manage creeping stress, you can take some basic relaxation measures like meditation or paced breathing.

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