They say a smile can brighten the darkest day. Now researchers think it can also extend your days.A study in the journal Psychological Science examined a database of professional baseball players and found those who put on a happy face in their official photographs � ended up living longer than those who didn't smile. Those with broad smiles lived an average of five years longer than players who didn't smile � reaching an average age of nearly 80. Those with partial smiles lived an average of 73 years.While psychologists have found increasing evidence that a positive outlook leads to a more stable and happy life, this is the first time they have linked smile intensity with lifespan.Psychologists say this makes sense but it doesn't necessarily mean people who don't smile a lot are facing a shorter life expectancy.Bottom line, it�s another indication that happiness is good for your health.