Respecting teenage friendships and relationships can take a lot of parental self-restraint. But this might make you feel a little better whenever Anika-of-the-Pink-Hair invades your home: a new 10-year study suggests teenagers’ friends have an important, positive effect on their mental health into adulthood.

“Our research found that the quality of friendships during adolescence may directly predict aspects of long-term mental and emotional health,” said study author Rachel K. Narr, a PhD candidate in clinical psychology at the University of Virginia. “High school students with higher-quality best friendships tended to improve in several aspects of mental health over time, while teens who were popular among their peers during high school may be more prone to social anxiety later in life.”

The study, published in the journal Child Development, followed 169 adolescents over 10 years, between the ages of 15 and 25. Though all American, the teenagers were racially, ethnically, and socioeconomically diverse. Once a year, they answered questions about their relationships with friends and participated in interviews and assessments that tracked anxiety, social acceptance, self-worth, and symptoms of depression; the teens’ close friends and peers were also questioned to corroborate teenagers’ reports.

Researchers found that teenagers who had at least one close friendship — that is, friendship with a degree of attachment and support that allows for intimate exchanges — at age 15 had lower social anxiety, a greater sense of self-worth, and fewer symptoms of depression by the time they reached age 25 than their peers. Conversely, teens who were broadly sought after in high school — that is, those who were popular among their peers, but perhaps not close to any one — had higher levels of social anxiety as young adults. (Neither having a strong best friendship nor being popular predicted any short-term changes in mental health; differences only became apparent later.)

While most of us eventually drift apart from the besties that define our teen years, study authors described the experience as self-confidence-boosting practice at social relationships — which is, after all, one of the primary developmental milestones of adolescence.

“Our study affirms that forming strong close friendships is likely one of the most critical pieces of the teenage social experience,” explained co-author Joseph Allen, a professor of psychology at the University of Virginia. “Being well-liked by a large group of people cannot take the place of forging deep, supportive friendships. And these experiences stay with us, over and above what happens later. As technology makes it increasingly easy to build a social network of superficial friends, focusing time and attention on cultivating close connections with a few individuals should be a priority.”

This jives with research into teen popularity, conducted by Mitch Prinstein, director of clinical psychology at the University of North Carolina-Chapel Hill earlier this year:

“It’s very lonely for them,” Prinstein said of teens whose popularity relies on broad consensus of their status, rather than their likability, in a June interview. “They report that they feel detached from others; isolated, like they can’t truly be themselves.”

While some teens who have high-quality friendships are also broadly popular, for most, the two might be mutually exclusive, Narr’s team suggested. Again, Prinstein’s work offers a possible reason why: “Because in order to maintain that status, they can’t show any vulnerability or make close connections,” he said. “People pay for that in the long run.”

So, no matter how much you hate their influence on your teen’s hairstyle, just remember your teen’s bestie is bolstering her mental health and teaching her how to build friendships (which is a developmental milestone for adolescents) at the same time. It’s a lesson that has to come from somewhere — and it’s probably not coming from you.