WHEN I MOVED TO BOSTON for graduate school, it took less than five minutes into the first orientation-day event for someone to crack a joke about the city’s unfriendly reputation. Local faculty and students swapped stories about bad drivers, rude pedestrians, and passive-aggressive train passengers. These were funny, but also concerning, since the latest research suggests that friendship is as essential to our overall health as diet, exercise, or sleep.
In recent years, studies that combine biology, psychology, chemistry, physics, and more have started to tell us just how much friendships — those positive and routine social interactions with people we like — significantly improve our lives. Having friends reduces stress and increases our tolerance for pain. Merely thinking of a friend can help us perceive a physical obstacle as less intimidating than if we evaluate the challenge alone. Friendships may even help us live longer. “These [findings] just seem to show up time and time again,” says James Coan, a neuroscientist at the University of Virginia who studies the impact of social relationships on the brain. “The more isolated you are, the more likely you are to die of anything at any time.”
Friendships play an essential role in regulating mood inside our brains. The hypothalamus controls things like hunger and sleep and produces oxytocin, a “feel-good” hormone stored in the adjacent pituitary gland. Friendly conversations release oxytocin, which imbues us with a greater social confidence to engage in other friendly conversations. But it can work the other way, too. Social isolation allows stress hormones like cortisol to proliferate, heightening our social inhibitions. Friendship is complicated by the potential for negative interactions like betrayal or feeling excluded, emotions that, if they make us angry, can cause cortisol levels to spike.
Beyond managing our moods, Coan believes that our brains evolved to rely on social resources like friendship. His Social Baseline Theory, published in 2015, argues that the human brain depends upon a sophisticated network of relationships to coordinate cognitive energies and accomplish shared goals, which he suggests is unique to humans. Unlike most primates, human beings are prepared to have multiple kinds of caregivers, and we tend to cooperate reflexively with one another from an early age. “We have huge brains that are incredibly metabolically expensive,” Coan says. “We’re not particularly good at physically defending ourselves compared to other mammals. Friendship is a fundamental feature of how we have been shaped by natural selection to continually adapt and survive.”
Although a cursory glance at these findings might suggest that we should amass as many friends as possible, quality is more important than quantity. Every new friendship means less time and mental bandwidth for your existing ones. There also appears to be an upper limit to the number of meaningful relationships our brains can sustain at any given time. British anthropologist Robin Dunbar pegs this threshold at roughly 150, with concentrically smaller inner circles of greater “closeness” (the most exclusive group comprising no more than five best friends).
Ironically, research into this field has gained momentum just as the rise of social media is complicating our traditional notions of friendship. The blurring of online and offline friends and acquaintances raises questions about the impact of social media on our ability to recognize a shared language of social cues. One study published last March by a team from MIT and Tel Aviv University sparked heated discussion when its results indicated that only half of our perceived friendships are mutual. The findings, though based on only one set of 23- to 38-year-old university students, assessing themselves within the context of the class they shared, nonetheless sparked anxiety that Facebook, in particular, was affecting our ability to sustain friendships in the physical world.
Coan remains cautiously optimistic about the potential for social media. “I think we’ll be surprised at how effective things like Facebook can be for social support,” he says, citing examples of online sub-communities that help people deal with traumatic issues like grief, chronic illness, or loneliness. One widely shared study from last fall, conducted in part by researchers at Harvard and Northeastern, suggested that people with a greater number of Facebook friends were less likely to die than less sociable counterparts.
But those same results revealed another surprise: The Facebook behaviors most closely associated with reduced mortality seemed to involve activity following face-to-face interactions, such as posting photos from a shared event. In order for our brains to reap the benefits of friendships, we seem to need some kind of real-world commitments.
“Part of the reason Facebook is so compulsive is that it’s so easy,” says Coan. “But liking someone’s baby photos isn’t enough to reap the rewards of an actual friendship. It requires an investment in other people, who can often be a pain in the butt to deal with.”
That is perhaps especially true in Boston, part of a region empirically shown to be the most irritable and neurotic corner of the country. Despite the stereotype, I’ve befriended some locals, for which I’m grateful. Bonus for me: Gratitude also releases oxytocin.
Matthew King is a nonfiction writer and graduate student in the MFA program at Emerson College. Send comments to firstname.lastname@example.org.