Happy people live longer.

It's a common assumption that happier people live longer, but the convincing data on this has not been easy to come by. Studies have offered widely different and competing findings - some finding no causation or reverse causation, others suggesting that unidentified, unobserved factors influence both happiness and longevity and health. Frey points to work by Diener and Chan showing that many kinds of studies, using different methods, conclude that happiness has a positive causal effect on longevity and physiological health. One of the studies noted by their survey is a meta-analysis based on 24 studies that estimates that happy people live 14% longer than persons who report that they are unhappy. In a survey of people living in industrial countries, happier people enjoy an increased longevity of between 7.5 and 10 years. Happier people are also less likely to commit suicide, and they are less often the victims of accidents...In longitudinal studies individuals are followed over many years, to identify whether the happier ones live longer. In the famous "nun study" researchers asked young women about their subjective happiness level before they entered a monastery. Those who perceived themselves to be happier died at a median age of 93.5 years. Those who considered themselves to be less happy died at a median age of 86.6 years.