ARI SHAPIRO, host:
Research suggests that friendships and social connections are important for maintaining mental health. Many of us formed our most enduring friendships at a time when we were quite vulnerable: the first semester of college.
For those who arrive on campus knowing few, if any, other students, researchers say there are two strong predictors of who will end up becoming friends. NPR's Allison Aubrey reports.
ALLISON AUBREY: On the day of his 19th birthday, Bipin Sen got on a plane in New Delhi and flew to Chicago to start an undergraduate program in engineering. He'd already determined his major. What he didn't know is who he'd live with once he arrived.
Mr. BIPIN SEN (Student): I had never been to the States, never been to Chicago, and knew no one in Chicago.
AUBREY: At some point during the long flight, he exchanged glances with another passenger, a guy about his age. It turns out once they arrived, they bumped into each other at the university housing office.
Mr. SEN: Sixteen hours later and 8,000 miles across, we had our first words of exchange. He was also an incoming freshman. He was in a different program, and just after talking for a few minutes, I asked if he wanted to just be roommates for the semester.
AUBREY: Lots of friendships begin with these chance encounters. Leila Holtsman and Sally Hoffmaster met 25 years ago, when they were assigned as freshman-year roommates at the University of Virginia.
Leila recalls her first impressions were that she and Sally were not so similar. Leila says she's short, and Sally…
Ms. LEILA HOLTSMAN: She's really tall. She's 6 feet tall. I remember amazed by her height and thinking that alone made us really, really different.
AUBREY: And Sally says their personalities were different, too.
Ms. SALLY HOFFMASTER: I was extremely shy, and she was more - definitely more outgoing.
AUBREY: In both these cases, what drew these friends together in the first place were proximity - being in the same place at the same time - and a common race or heritage. So are these two factors really enough to spark a friendship? Bruce Sacerdote, a researcher at Dartmouth College, says the answer seems to be yes.
Professor BRUCE SACERDOTE (Researcher, Dartmouth College): I think having that shared background and that random chance meeting certainly have big impacts on who your friends are, and I think have also big impacts on who you marry, where you live, what you do.
AUBREY: Sacerdote explains a lot of sociology research points to this proximity or distance effect, including his own study. He analyzed the volume of email exchanges among students on his campus, and correlated the number of emails with factors such as race, hometown...
Prof. SACERDOTE: Whether you went to a private or public high school, what fraternity you were in, and distance - your freshman year distance, which is by and large randomly assigned here.
AUBREY: And you found that this race and distance seemed to be critical?
Prof. SACERDOTE: Huge.
Prof. SACERDOTE: Right. They are the big determinants.
AUBREY: Of course, things such as interests and hobbies are also important. It's pretty common for friendships to be fluid. And clearly, students of different races do mix on campus. Once Bipin and his roommate developed a wider, more diverse circle of friends, they branched off in different directions.
But in the case of Sally and Leila, they became each other's rock. Sally says Leila helped her come out of her shell a bit. For instance, when they walked down the campus quad, Sally used to look down at the ground because she was too shy to make eye contact.
Ms. HOFFMASTER: And I'd be walking with her and she's like, hit me in the stomach and remind me to like, you know, look up.
AUBREY: And connect with people. Sally says it made her realize that Leila had her back, that a best friendship was evolving.
Dr. GREG EELLS (Psychologist, Cornell University): We tend to like people who kind make up for some of the deficits we see in ourselves or help us kind of grow in ways that are not our strengths. So yeah, I think that's very typical.
AUBREY: That's psychologist Greg Eells of Cornell University. He says college roommates have a lot of face time, which can help develop trust and intimacy.
Dr. EELLS: There is something about those relationships you can form in college. It can be lifelong sources of support.
AUBREY: Leila and Sally say two and a half decades later, they're still best friends. And Sally says that when she meets someone new today, she has no problem making eye contact at all.
Allison Aubrey, NPR News.
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SHAPIRO: You can learn more about how friendships factor into the mental health of college students in this week's Your Health podcast. It's online at npr.org/health.