Your friends may know you better than you know yourself. Personality traits you display in your 20s hold clues to how long you??ll live??? and your friends can judge these traits better than you, researchers report in the journal Psychological Science.

??Friends are better predictors of your longevity than you are,?? says Madeleine Leveille, adjunct professor of psychology at UConn??s Avery Point campus. Or at least they have more insight into your personality traits.

Using personality data from a study that was begun in 1935, a team of researchers including Leveille found that men rated highly conscientious, as determined from the averaged reports of five close friends, lived longer than men rated as less so. For women, agreeableness and emotional stability were associated with longer lifespans. The effects of these personality traits were quite clear ?? as strong as the correlation between smoking and lung cancer, says Jim Connolly, a forensic psychologist who co-authored the paper.

The researchers don??t know why conscientiousness is so strongly linked with longevity in men. It may be that men who are conscientious are more likely to exercise and eat well and avoid risky behavior. For women, agreeableness and emotional stability may allow them to avoid the negative health consequences of depression and anger.

It may also have had something to do with the times during which the study subjects lived, Connolly says. The women of this generation would have come of age during the 1920s and been young wives just as the Great Depression began who did not work outside the home, in order to preserve jobs for men. During the war years of the early 1940s, this all changed; the women would have been expected to go to work and manage households of children at the same time. And then during the late 1940s, they would have been under social pressure to leave the paid workforce to be housewives again. A flexible, agreeable personality might have been helpful in cushioning the many changes these women lived through.

Connolly and Leveille suggest that if the study were to be repeated now, when men and women have less gendered life experiences, conscientiousness might be just as important for predicting longevity in women.

Psychologists have known that personality traits have some effect on life span, but this was the first study to show such a strong, unambiguous connection. The key difference between this study and others is the use of personality assessments done by close friends, instead of by the participants themselves.

??You expect your friends to be inclined to see you in a positive manner, but they also are keen observers of the personality traits that could send you to an early grave,?? says Joshua Jackson, assistant professor of psychology at Washington University.

Jackson brought his expertise in statistical analysis to the team, and also his relative youth ?? Connolly and Leveille plan eventually to turn over custody of the data set to him so he can take it into the next generation, getting in touch with children of the original participants. They hope to track the effects of personality traits and divorce into the second and third generations.

The study is one of the longest-running ever to link personality and mortality. It was begun in 1935 by E. Lowell Kelly, a professor of psychology at UConn at the time. Kelly was primarily interested in how personality affected divorce rates. But the detailed data on personality allowed Kelly and the researchers he collaborated with to subsequently look at other ways personality may influence a person??s life.

Connolly, Leveille, and Jackson are currently using the same study to do an analysis of altruism and longevity. So far, they??ve found that the good do not die young ?? and neither do their spouses. They say this research should be?ready for publication?sometime later this year.