At some point, you've probably heard someone joke about how a stressful event is turning their hair gray. You probably took this in as a figurative statement. The person who said it probably intended it that way, too. However, new studies show that stress can indeed turn one's hair gray--and even more interestingly, undoing the causes of that stress can sometimes also restore the hair color. A new study from Columbia University Vagelos College of Physicians and Surgeons is th