Frey, B. S. (2011). Happy People Live Longer. Science 331, 542
There is a longstanding idea that happiness causes people to live longer, healthier lives. However, convincing evidence that subjective well-being (the more scholarly term for happiness) contributes to longevity and health has not been available. Recently, however, social psychologists Diener and Chan ( 1) showed that many kinds of studies, using different methods, conclude that happiness has a positive causal effect on longevity and physiological health.