You don't need a doctor or an array of medical tests to know how long you'll live-your friends can tell you.
Even when you're in your 20s, your friends can predict whether you'll make it to 75, and they are uncannily accurate.
The tell-tale signs that friends see but we often don't pick up on vary between the sexes: for men, those who are more open and conscientious tend to live longer, while for women it's their degree of agreeableness and emotional stability.
These traits suggest the men will eat a healthy diet, stick with exercise and avoid risks, and the women will be better equipped for fighting off depression, anxiety and anger.
The insights of friends as predictors for longevity have been discovered in one of the longest studies in psychology, one that began in the 1930s when the participants were in their mid-20s, and most of whom were engaged to be married. Personality traits, which included the views of friends as well as the subjects themselves, were documented, and their deaths were also recorded.
"You expect your friends to be inclined to see you in a positive manner, but they are also keen observers of the personality traits that could send you to an early grave," said lead researcher Joshua Jackson from Washington University in St Louis.
(Source: Psychological Science, 2015; doi: 10.1177/0956797614561800)