April 25, 2017 12:56 PM EDT

Best friends are great for celebrating the good times, but a new study suggests that their biggest emotional boosts may come when the going gets tough. Researchers say the preliminary analysis provides the first long-term evidence that having a close, non-romantic relationship can be enormously beneficial for adults’ psychological health.

The new research will be presented at the British Psychological Society annual conference in May. (It has not yet been published in a peer-reviewed medical journal.) Lead author Rebecca Graber, PhD, now a senior lecturer at the University of Brighton in the U.K., conducted the study while at the University of Leeds.

To study the relationship between friendship and psychological resilience, Graber and her colleagues recruited 75 men and women through websites, campus events, and community organizations that support socially isolated adults. The participants were asked about their ability to bounce back from challenging life scenarios (like a divorce, chronic illness, or death of a loved one), their coping behaviors and self-esteem, and their relationship with the person they considered their “best friend.”

A year later, they were asked the same questions over again. After controlling for prior levels of resilience, the researchers found that “the greater the quality of the participants’ best friendship, the more resilient they were one year on,” Graber told RealSimple.com via email.

The study couldn’t prove that better friendships actually caused greater resilience. But because of its year-long design, it was able to show the direction by which one predicted the other. In other words, it wasn’t simply a case of resilient people having better friendships in the first place.

Why, exactly, BFFs promote resilience remains an unanswered question, says Graber. None of the potential mediators she included in the study (such as self-esteem and coping mechanisms) appeared to have significant effects on the results. The next step, she says, will be to replicate this study and explore, in more detail, these and other potential factors.

Surprisingly, people who reported better friendship quality had higher levels of resilience, regardless of whether they kept the same best friend over the course of the year. “I think this raises important questions for psychologists about whether we overemphasize friendship stability,” says Graber. “We tend to view friendships as these unchanging relationships, when really it is fairly common to have ebbs and flows.”

And while Graber specifically asked participants about their best friend other than siblings or spouses, she says that 79 percent of people first identified a brother or sister—and 57 percent first identified a romantic partner—as the person they considered their closest friend.

“Whether it is important to have a best friend outside your romantic relationship would be a good avenue for future research,” Graber says. “As my thinking develops, I am increasingly convinced that what is important is how your social relationships align with your needs.”

Graber’s previous research has shown that having a best friend appears to encourage resilience in children; now the benefits for adults have been documented, as well.

“The research suggests that friendships do help us get through difficult times,” says Graber. “That is something many of us (including myself) believe intuitively, but it is not reflected in many aspects of culture nor in how we structure society and economic systems in the Western world.”

She says that communities and policymakers should look for ways to increase opportunities for adults to cultivate friendships—especially adults who are socially isolated, like caregivers or people with mental health problems.

And on an individual level, she adds, we should appreciate our bosom buddies for the unique benefits those friendships can provide—the ones that romantic, family, and work-related relationships can’t.

At the same time, Graber adds, you don’t not need to be a social butterfly. “My analysis shows that just one good quality friendship can make a difference to how you get through difficult times,” she says. “We are not all extraverts, and we don’t need to be. I would encourage people to make time to value and prioritize their friendships—especially when life gets hard.”

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