For a long time, anecdotes and urban legends have connected the experience of stress with the phenomenon of hair going gray. In 2020, for the first time, Harvard University scientists discovered exactly how the process plays out: they found that stress activates nerves that are part of the fight-or-flight response. This actually causes permanent damage to pigment-regenerating stem cells in the hair follicles.
But in order to find out how this works, scientists had to narrow down the culprit. Since stress affects the whole body, scientists needed to determine which body system linked stress and hair color. First, scientists ruled out the possibility that the link could be an immune attack on pigment cells or that it could be an overabundance of the stress hormone cortisol.
Then, the researchers considered the sympathetic nerve system. Sympathetic nerves branch out into each hair follicle on your skin. These nerves also release the chemical norepinephrine. Nearby stem cells that are meant to later become pigment cells take up the norepinephrine, and when that happens, the chemical activates the body to overuse these stem cells. Then, the body has no reservoir of cells that it can use to regenerate hair color. Basically, in times of acute stress, the body depletes its store of cells that could be used to regenerate hair color. Once these are gone, the hair goes gray.But no one’s hair turns gray overnight. Reducing stress can prevent damage to tissues which aren’t outwardly visible but are vital to our body and its ability to repair and heal itself.