Your best friends know your favorite band and brunch place and exactly what movie will cheer you up. Sometimes, you may even feel like they know you better than you know yourself. Now, research suggests they might be able to accurately predict some pretty big things — like how long you'll live. We've known for a while now that there's a link between personality traits and lifespan. This new study, published online earlier this month in the journal Psychological Science, wanted to take that a step further by looking at whether our friends' ratings of our personalities can more accurately predict our mortality risk than our own self-ratings can. To do so, the researchers used data from a 75-year study observing 600 participants through 2013. The data included participants' self-ratings and their friends' ratings of their personalities. Although the original information was collected using a somewhat outdated personality assessment, the researchers were able to match up the responses to the Big Five traits that are often used now. They were also able to verify the participants' times and places of death through the Social Security Death Index and individual state indices. Their results showed that women who were rated by their peers as being more emotionally stable, agreeable, courteous, and sincere had a 15% reduced mortality risk. For men, mortality risk went down if they were rated by their peers as more open, conscientious, persistent, reliable, and intelligent. Overall, the researchers note, "friends’ ratings were better predictors of longevity than were self-reports of personality." Of course, because these are correlational data, there's certainly not enough to say that personality traits can predict your death. But, previous studies have shown that being more agreeable, open, and conscientious may be related to living a healthier life. This is perhaps because those people are more likely to do things like listen to a doctor's advice. So, if you're worried, it might be worth a chat with your friends — they could be better for your health than you even realize.