Legends from around the world feature characters whose sadness turns their hair grey overnight. Bizarre as they appear to be, those stories actually include an element of truth. Researchers at Harvard University confirmed that stress can indeed lead to grey hair and discovered the reasons behind it.

In a study published in Nature, the authors found that the nerve cells involved in the fight-or-flight response cause permanent damage to the pigment-regenerating stem cells in hair follicles in mice. This finding advances our understanding of how stress impacts the hair, moving researchers one step closer to blocking its negative effects.

To discover the cause of grey hair, researchers tested and eliminated different possible sources. They initially hypothesized immune attacks on pigment-producing cells were the cause, but mice without immune cells were still susceptible to grey hair.

They proceeded to other theories such as cortisol, the hormone elevated by stress. The theory of cortisol was disproved by further experiments on mice. After the mice lost their abilities to produce cortisol, they could still grow grey hairs under stress.

After several rounds of the process of elimination, the scientists landed on the sympathetic nerve system, which is responsible for the body's fight-or-flight response, as the culprit. Sympathetic nerves branch out into every hair follicle on the skin. When stressed, the nerves will release chemicals that are taken up by nearby stem cells, activating them into pigment-generating cells used to color the hair. An excess amount of pigment-generating cells will be activated when under stress, and the pigment reservoirs of these cells will be prematurely depleted. Once depleted, there are no longer cells that can color ones hair.

This finding helps scientists move towards moderating or blocking the effects of stress. In stressful environments, people are going to get grey hair at an earlier age. Currently, there are over 1.5 million posts with the hashtag #Greyhair on Instagram, and research in 2018 shows that 32 percent of British women under the age of 30 have already started to go grey. Indeed, grey hair is beginning to impact even those in their 20s. Even though factors like nutrition, medication, and genetics also play essential roles in greying hair, stress might have the greatest impact overall.

The relationship between stress, hair, and stem cells could also lead to new discoveries about how stress affects organ functions and blood vessels in comparison to stem cells. Scientists across many disciplines hope to ultimately exploit this relationship to find a way to control stem cells.

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Stressful situations cause grey hair - CMU The Tartan Online