"Hell is other people," wrote the French existential philosopher Jean Paul Sartre, in one of his most famous lines from Huis-clos (No Exit). Half a century later, research has shown exactly the reverse may be true.
In a study of 4,739 adults whose happiness was monitored over 20 years from 1983 to 2003, doctors found that close physical proximity was a key factor in the spread of happiness; it is, in effect, contagious. A friend who becomes happy and lives within a mile increases your own likelihood of happiness by 25 per cent. But if they live more than a mile away there is no effect. Previous research has shown that people can "catch" each other's moods by "emotional contagion", through copying facial expressions or other bodily activities. Students assigned to share with a depressed room-mate become depressed themselves, while waiters who provide "service with a smile" see the benefits in the size of their tips, the study in the British Medical Journal showed. In the study, researchers from Harvard Medical School and the University of California found the biggest boost to happiness came from living next door to a happy neighbour, increasing the chances of happiness by 34 per cent. This was much greater than the effect of other neighbours in the same block. The importance of physical proximity suggests frequent social contact may be more important than deep social connections to the spread of happiness. But spouses have a smaller effect; you have an 8 per cent higher likelihood of being happy if your partner is.