When you smile, your brain releases tiny molecules called neuropeptides to help fight off stress. Then other neurotransmitters like dopamine, serotonin and endorphins come into play too. The endorphins act as a mild pain reliever, whereas the serotonin is an antidepressant. One study even suggests that smiling can help us recover faster from stress and reduce our heart rate. In fact, it might even be worth your while to fake a smile and see where it gets you. There’s been some evidence that forcing a smile can still bring you a boost in your mood and happiness level.