Baby Monkey Gangs Reveal Genetic Effects of Loneliness

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Loneliness isn’t just a state of mind. It also affects our bodies. A growing number of studies are showing that a feeling of loneliness is associated with heart problems, viral infections, and an increased risk of death.

And those health problems, in turn, are associated with huge differences in gene activity. Some genes, like ones involved in inflammation, are more active in lonely people. Others, such as genes that code for antiviral defenses, are less active.

But human studies don’t reveal whether there’s a direct cause-and-effect relationship between loneliness and the changes in gene activity. (Researchers wouldn’t try to make humans chronically lonely just to find out.)

That’s why physiologist Steve Cole of UCLA turned to rhesus monkeys for an answer.

Cole and his colleagues had some baby monkeys grow up in “gangs” of other youngsters. Without a mother to offer a safe home base, the monkeys spent a lot of time clinging to each other. They didn’t explore their environments as much as normal babies (raised by moms), and they got into more fights, suggesting that they were experiencing some sort of social stress.

When Cole’s team looked at these monkeys’ genetic signature, they found that it resembled that of human loneliness. There was evidence of increased inflammation and decreased immunity to viruses. When the researchers gave the monkey kids a fake mom—a mere cloth-covered wire basket—their genetic functions started to ease back toward normal.

So why would our bodies change our immune system in response to social stress?

Cole, who presented the results on February 18 at the AAAS meeting, thinks that when we’re interacting normally with friends and family and feeling safe, our bodies are prepared to tackle virus infections because we’re most likely to get infected during social interactions. 

But if we’re feeling stressed or lonely, our bodies may anticipate injury (through attacks by predators, for example) and the bacterial infections that invade the wounds. Thus they might turn down the antiviral genes and save energy to fight bacteria instead.

These results are just one example of the ways our environment can tweak body chemistry.

Culture is among the environmental factors that can also have an impact. A study published last year, for example, found that Americans who have a gene associated with empathy tend to talk about their problems—whereas Koreans with the same version of the same gene would rather bottle up their stress.

Although our genes aren’t going to change, it’s becoming clear that our genetic instruction manual is “open to advice” from the outside world, Cole says. “The world gets inside us.”

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