Whether you view it as a sign of aging or a sign of wisdom, gray hair is inevitable for most people. For some, it happens at a much earlier age than for others. Some of the most common reasons for premature graying include stress, a medical condition such as thyroid disease, vitamin deficiency, nicotine use and genetics. While premature graying may be frustrating, scientists say they have finally figured out how stress plays a role.
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In a study published in the journal Nature, researchers injected a compound into mice to elicit a stress response. Within five days, their fur was white. The research team looked at the immune system and the stress hormone cortisol as potential causes, but neither was responsible for the color change.
The scientists discovered that part of the rodent’s nervous system was depleting pigment cells from hair. Melanocyte stem cells in hair follicles color hair by converting into pigment-producing cells, which the body cannot replenish. Once these cells are gone, hair color essentially vanishes. The compound injected into the mice triggered the sympathetic nervous system to release a neurotransmitter called norepinephrine. As a result, stem cells in the mice were over-activated, and melanocyte cells began rapidly converting into pigment-producing cells, using up the stem cell supply.
The sympathetic nervous system controls the body’s fight-or-flight response to stress. The study’s findings provide a new look into the link between stress and gray hair.
Melanocyte cells are also responsible for skin color. Lead study author Dr. Ya-Chieh Hsu explained, “We now know for sure that stress is responsible for this specific change to your skin and hair, and how it works.” She added, “"I expected stress was bad for the body, but the detrimental impact of stress that we discovered was beyond what I imagined. After just a few days, all of the pigment-regenerating stem cells were lost. Once they're gone, you can't regenerate pigment any more - the damage is permanent."
If your hair turns gray before you’re ready, you may be tempted to dye it. But considering the amount of toxic chemicals in hair dye, you may want to embrace it instead.