How Long Will You Live? Ask Your Friends

In the quest to understand human mortality, people turn to just about any available resource. The truly concerned will devour medical news, tinker with complex life expectancy calculators and pester the family doctor as if she were clairvoyant. But research out of Washington University in St. Louis suggests a simpler method may work best: asking your friends.

A recent study in Psychological Science posits that someone's personality in their 20s can have a significant bearing on long-term physical health and longevity. The study also notes that friends possess tremendous insight into each other's personalities—your closest pals probably know you better than you know yourself.

“Really simple ratings of your personality … predict decades in advance how healthy you’re going to be and how long you’re going to live,” says Joshua Jackson, the assistant professor of psychology who led the study. In particular, friends’ ratings frequently pick up on traits we ignore, Jackson adds. “Maybe you are purposely blind about negative aspects of your personality that would lead to a shorter life.”

To carry out the research, Jackson and his co-authors dusted off a dormant study started in the 1930s, in which some 600 participants sounded off on their friends’ personalities. The researchers then tracked the participants across decades, matching the personality assessments to their years of death. The study centered on what the original researchers dubbed the “Big Five” traits—conscientiousness, extroversion, agreeableness, neuroticism and openness. “These five personality characteristics really capture the important ways people differ,” Jackson says.

While friends weren’t able to predict a precise time and cause of death—78 years old, diabetes—their assessments provided valuable insight into who lived the longest. Two traits in particular, conscientiousness and neuroticism, are likely to have the greatest impact on life span, the team concludes.

Conscientious individuals fared better in the study, perhaps because they tend to be more orderly, hard workers who pay attention to health advice. “You’re predicted to live seven-and-a-half years longer if your friends see you as higher in conscientiousness compared to those that see their friends lower,” Jackson says. More neurotic individuals are plagued by heightened worry and anxiety, and they tended to live shorter lives. 

Benjamin Le, an associate professor of psychology at Haverford College in Pennsylvania, echoes Jackson’s findings that friends can see things people miss in themselves. “Outsiders have a more accurate view because their perceptions aren’t colored by self-serving biases,” he says. “When I look at myself, I have to maintain my self-esteem,” but a friend doesn’t need to preserve that rosy perspective.

There are a few degrees of separation between personality traits and longevity, though, says Benjamin Karney, a professor of social psychology at the University of California, Los Angeles. Simply being impulsive won’t shorten one’s life, he says. But unless you are aware of your impulsivity and know how to keep it in check, you are more prone to actions like giving in to the urge to smoke a cigarette or devour a slab of pound cake, and that can impact your health.

And what does a medical doctor think of the study? Marcela Dominguez, a family physician in southern California working with SignatureMD, says that she regularly pays heed to patients’ temperaments. “In order to connect with patients, we have to factor in their personality,” she says. Dominguez also agrees that friends can be valuable yardsticks when gauging a patient’s health. Too often an aloof patient is led to her office by a rightly concerned friend or family member. “People are coming in as a consequence of other people having a little bit more concern for their health,” Dominguez says.

To test Jackson’s findings in the wild, I asked three of my closest comrades to assess my Big Five traits. The risk-reward ratio was steep. At best, I’d receive results that hint at a long life. At worst, I’d endure predictions of an early death—and harsh evidence that maybe I’m not as likeable as I think. But I cobbled together the survey and clicked “send.”

Mercifully, the results weren’t too distressing, and they were consistent. All my friends agree I’m less extroverted than the average person but more conscientious and neurotic. (“Don’t be offended by my answers!” one friend pleaded, ranking my neuroticism as 9 on a scale of 10.) It seems in my quest for a long life, prudence and anxiety will be locked in a perennial struggle.

So is it worth sharing the poll results with my physician? Jackson says it might be. “We could utilize these personality assessments to obtain a more personalized medicine,” he says. I’ll keep that in mind next time I’m seated on an examination table.