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Good friends aren’t just good for a shoulder to lean on in tough times. Studies have shown for at least 40 years that having social support can protect against heart disease, cognitive decline, and even death. But new research suggests it’s not just about having friends in the moment: The depth and consistency of a person’s relationships over a lifetime have a huge impact on their health—and is even written in their DNA.
For the new study, researchers compared social experiences across the lifespan of more than 2,100 middle-aged adults in the United States to the biological clock embedded in their DNA. The hands of these biological clocks consist of epigenetic changes to DNA—specifically, patterns in the addition of a chemical called a methyl group to certain genes. Such methylation doesn’t cause mutation; rather, the process turns the gene on or off in different cells of the body at different times. Over time, methylation patterns on certain genes change and can be used as markers of biological aging, a measure of how rapidly cells wear down that can be faster or slower than aging by the calendar. An older biological age is a strong predictor of chronic disease and early death.
The researchers measured social connection in a variety of settings over time to show that people with more social activity and sincere, long-lasting relationships aged more slowly. “We found that the depth and consistency of social connection, built across decades and different areas of life, matters profoundly,” says Anthony Ong, a psychologist at Cornell University. “Strong and sustained social networks appear to actually set back a person’s biological clock.”
“It’s not just the number of people that you are connected to, but how close you are to them that really matters.”
Ong’s team also reported that people with less social connection had higher levels of an inflammatory molecule that promotes heart disease, diabetes, and neurodegeneration.
One strength of the new study is that it considers lifelong social connection in a holistic way, says Courtney Boen, a sociologist at Brown University who was not involved in the study. Most researchers who analyze the health effects of social connections look at more specific and short-term measures, Boen says, such as how many friends they have or whether they feel supported by their local community. But Ong’s team captures a bigger picture by looking at social ties experienced in four domains: family relationships in childhood, religious life, emotional support, and community engagement. They measured this by asking subjects questions like: “How much affection did your mother give you?” “How often do you seek comfort through religious or spiritual means?” “How often do you receive emotional support from friends and family?” and “Do you believe that people are kind?”
The researchers didn’t break down how each of these domains might be linked to biological aging individually. “I’d like to see all these separately,” says Kathleen Mullan Harris, a sociologist at the University of North Carolina at Chapel Hill who was not involved in the study. For example, Harris says she doubts that DNA methylation affected by parental relationships in childhood still has a large direct impact on biological age in adulthood. Rather, she thinks it’s more important how those relationships prime people to connect with others later in life.
Still, the study clearly suggests that social connection, viewed holistically, is linked to a younger biological clock. To stay connected, Harris recommends joining institutions that already exist in your community. This could include a wide variety of groups, like schools, religious organizations, volunteer clubs, or sports teams.
Boen recommends focusing on quality over quantity when choosing who to make friends with, and which friendships to invest in. “Superficial ties tend to matter less than deeper ties,” she says. “It’s not just the number of people that you are connected to, but how close you are to them that really matters.”
Carving out space for meaningful social connection can be difficult in a world where responsibilities and distractions compete for precious free time. But it may be worth thinking about it in a new way. “Social connections are a lifelong investment for profound physical health benefits,” Ong says. “Aging well isn’t only about staying physically healthy; it’s also fundamentally about staying connected.” 
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Lead image: HilaryDesign / Shutterstock
