Your mom suggested it, oh, about a thousand times. And there is scientific evidence that smiling can help the body and mind recover from stress. In a study published last year in the journal Psychological Science, researchers induced stress in 170 students by asking them to perform a dexterity test and then plunge a hand into ice water. When the subjects were made to smile during these tasks, their heart rates returned to normal levels more quickly after they recovered from the stress. They were also better at maintaining positive feelings during the plunge than were those who held neutral expressions. Moreover, scientists observed an even greater drop in heart rate when students broke into a “Duchenne smile” (the type of smile that engages the eyes and the mouth). “Smiling can jump-start the process of happiness,” says Jeff Brown, a Harvard psychologist and the author of Chicken Soup for the Soul: Think Positive for Great Health ($10, amazon.com). “When you smile, you trigger a psychological and neurobiological alignment with positive emotions, and that can lead to healthier living.” In other words: Fake it till you make it.