If you’ve seen the before-and-after photos of U.S. presidents, you know that job stress likely causes gray hair. Modern presidents from Lyndon Johnson to George W. Bush to Barack Obama have entered Pennsylvania Avenue with dark heads of hair only to depart in haloes of gray. But the connection to stress had not been proven in a lab, due to the difficulty of correlating moments of stress with hair pigmentation.
Researchers at Columbia University dove into the crosshairs of this longstanding mystery and developed a new way to image human hairs that captures slices of about 1/20th of a millimeter—the equivalent of one hour of growth. They then analyzed the hairs of 14 participants over time, and cross referenced them with entries that participants kept in stress diaries. They found direct correlation between gray patches and stress. Their work was published yesterday in eLife.
Hairs, it turns out, have variations in color, especially at high magnification. “When hairs are still under the skin as follicles, they are subject to the influence of stress hormones and other things happening in our mind and body,” says coauthor Martin Picard, an associate professor of behavioral medicine at Columbia University’s Vagelos College of Physicians and Surgeons. “Once hairs grow out of the scalp, they harden and permanently crystallize these exposures into a stable form.”
Pivotally, the researchers found that some participants’ gray hairs naturally reverted to their prior color when lifestyle stressors dissipated. One participant went on vacation, and five hairs returned to dark color during the holiday. Once beyond the scalp, the hair cannot change color, but newly growing hair in the follicle can. The effect is thought to be from stress changes in mitochondria, and you can see what it looks like in a video here.
Don’t get too excited about transforming a fully gray head with the power of rest and relaxation. Factors including age, health, and genetics also impact the threshold at which hairs turn gray. “We think hair needs to reach a threshold before it turns gray,” Picard says. “We don’t think that reducing stress in a 70-year-old who’s been gray for years will darken their hair or increasing stress in a 10-year-old will be enough to tip their hair over the gray threshold.” But for the decade-plus that many of us dance around that threshold, less gray may be feasible if your boss and family stay out of your hair.
Though you may be reading this wondering whether you can reclaim your pre-pandemic hair color (you probably can!), the researchers say that their study has wider implications. “Understanding the mechanisms that allow ‘old’ gray hairs to return to their ‘young’ pigmented states could yield new clues about the malleability of human aging in general and how it is influenced by stress,” says Picard. “Our data add to a growing body of evidence demonstrating that human aging is not a linear, fixed biological process but may, at least in part, be halted or even temporarily reversed.”