The July issue of Proceedings of the National Academy of Sciences posted an article by UCLA and the University of North Carolina showing that different types of happiness have surprisingly different effects on the human genome. Narcissistic happiness, like prolonged stress, causes high levels of inflammation and low antiviral and antibody gene expression. On the other hand, the happiness generated by making someone else happy lowered the level of inflammation and strong expression of antiviral and antibody genes.
It seems that there is a natural selection for those people who give, share, and love rather than those who are hedonic and not particularly interested in the happiness of others.
