When you're smiling, the whole world really does smile with you. A paper being published Friday in a British medical journal concludes that happiness is contagious — and that people pass on their good cheer even to total strangers. American researchers who tracked more than 4,700 people ...

Are your friends “making you fat?" Or “keeping you slender?" According to new research from Harvard and the University of California, San Diego, the short answer on both counts is "yes." A study in the July 26 issue of the New England Journal of Medicine suggests that obesity is "socially contagious," spreading from person ...