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Zebrafish show less fear when they are among familiar fish.

Source: iStock/FionaAyerst

The presence of a friend can lower stress levels. That’s an established phenomenon known as “social buffering.” Given how lethal stress can be, this is very good to know. But exactly how do friends calm us down? Does it matter which friend? And under what circumstances? Scientists are exploring these open questions in everything from fish to 15-year-olds. A series of recent studies provide some interesting new hints to better explain the power of social connection.

A shoal of zebrafish wouldn’t be the first place you’d think to study friendship and stress. But a team of Portuguese researchers led by Rui Oliveira did just that. They placed fish in tanks alone or with other familiar fish, and then injected a substance known to be alarming into the water. The zebrafish showed reduced levels of fear—they froze less—when they could smell the presence of familiar fish and even lower levels if they could see their “friends.” This marks the first time anyone has found evidence of social buffering in fish. It suggests that the phenomenon is so important to survival that it has distant evolutionary origins shared by many different species. And furthermore, the researchers believe zebrafish brains hold clues to how exactly friendship eases stress in humans. In the presence of the shoal, the fish showed patterns of brain activation very like those seen in mammals with friends.

iStock/Dodge65
Source: iStock/Dodge65

For chimpanzees (and humans, for that matter), a friend is an individual with whom there is a long-standing, cooperative bond. A recent study led by Roman Wittig and Catherine Crockford at the Max Planck Institute for Evolutionary Anthropology in Germany investigated two possibilities. Did the presence of friends mainly help animals weather stressful experiences (like coming across a neighboring group of chimps)? Or did it make a difference to their well-being in a more everyday way, such as when they were grooming each other? The researchers measured stress-related hormones (glucocorticoids) in the chimps’ urine in both situations, as well as when the animals were not socializing. Hormone levels were lower whenever friends were together, and the difference was most pronounced in the most stressful situations. But overall, the researchers found evidence that regular time spent with friends led to better routine health. The benefits of social buffering, in other words, aren’t limited to moments of acute stress.

Chimpanzees and humans share a neurobiological set-up called the hypothalamic-pituitary-adrenal (HPA) axis, which is ground zero for stress responses. Imagine that you are preparing to give a speech to a large crowd. That’s enough to induce stress in most of us, and trigger a cascade of hormones along the HPA axis. The end result is that cortisol levels in the blood rise. Higher cortisol levels get you revved up to perform, but can be harmful over time. Being with friends lowers the levels of cortisol and other stress-related hormones.

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Mothers are the best social buffers for children, lowering stress levels and helping them cope.

Source: iStock/bmcent1

In humans, scientists are investigating how and when stress responses develop. For young children, mothers (or other close caregivers) are the best social buffer there is. Kids put in a stressful situation show more mature regulation of brain activity when their mothers are with them. But how does that response change as kids grow older? That’s what neuroscientist Dylan Gee wanted to know. Formerly at the University of California, Los Angeles and now at Yale, Gee studies how brain circuits mature. As in so many other things, in her study, puberty turned out to be a turning point for dealing with stress. For adolescents, Mom’s presence no longer helps to reduce stress. On the other hand, the necessary brain circuitry to be able to manage the stress—a network that connects the amygdala to the prefrontal cortex—is more fully developed in teenagers. Gee and her colleagues think that perhaps there’s a window of time in childhood during which the positive effects of social buffering are etched into the brain.

It seems logical that when parents no longer serve as social buffers, friends might take over. But that’s not what a recent study from the University of Minnesota found. The researchers induced stress in 15- and 16-year-olds using a common test that combines stressors like public speaking and mental arithmetic. They found that the presence of friends did not reduce stress. In fact, cortisol levels went up compared in response to friends versus parents. Perhaps for hyper socially conscious teenagers, having peers around is a mixed blessing because it adds peer pressure.

By adulthood, however, friendship is a proven and reliable source of stress relief. Teenagers notwithstanding, the balance of the evidence is clear: If you’re feeling stressed, call a friend.

References

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