Scientists have found out why stress makes hair gray

Laverne Higgins
January 23, 2020

"It also gives us an idea of how stress might affect many other parts of the body", she said. "We wanted to understand if this connection is true, and if so, how stress leads to changes in diverse tissues".

"It's turning my hair grey" is a common expression used to denote stressful periods in our lives, but up until now we didn't realise it held any scientific backing. They hypothesized that there was a cortisol link or that it was related to an immune attack on cells but found both of those premises to be false.

In experiments on mice, stem cells that control skin and hair colour became damaged after intense stress. But once more, it was a dead end.

Before this new research, not only was it a mystery as to how hair turns gray in times of stress, many scientists even questioned whether stress could actually directly cause hair to turn gray. She chemically induced stress in mice by injecting them with a compound called resiniferatoxin, which boosted the animals' stress hormone levels; this method provided a reliable way of inducing the stress response over other strategies that the team explored, including using restraints, tilting the animals' cages, wetting their bedding and changing their lighting conditions.

It might not come as a shock to learn that stress can turn your hair gray, but a team of Harvard scientists recently discovered the surprising reason why.

Although fight-or flight is generally a beneficial response, it also shuts down many systems in the body that it does not deem beneficial to survival, such as reproduction.

Sympathetic nerves stimulate hair follicles - for example, they're responsible for the goosebumps we get due to a scare or a cold breeze.

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Within the hair follicle, sure stem cells act as a reservoir of pigment-producing cells. "But when they are exposed to norepinephrine from the sympathetic nerve, all of the stem cells are activated and convert into pigment-producing cells", said Ya-Chieh Hsu, associate professor of stem cell and regenerative biology at Harvard University and a Harvard Stem Cell Institute principal investigator. The stem cells all convert into pigment-producing cells, prematurely depleting the reservoir.

"I expected stress was bad for the body", said Prof Hsu.

The team says that once all the pigment-regenerating stem cells are lost, you can't regenerate pigments anymore, and the damage is permanent. This is perhaps one of the only negative side effects of it. "Nonetheless in this case, acute stress causes eternal depletion of stem cells", acknowledged postdoctoral fellow Bing Zhang, the lead creator of the look.

The collaborators included Isaac Chiu, assistant professor of immunology at Harvard Medical School who studies the interplay between nervous and immune systems.

"All and sundry is conscious of that peripheral neurons powerfully grasp an eye on organ feature, blood vessels, and immunity, but less is significant about how they retain an eye on stem cells", Chiu acknowledged.

But, as it turns out, the specific type of stress associated with the brain's fight-or-flight response is the culprit behind graying.

The scientists hope that their research will help illuminate the wider effects of stress on different organs and tissues and clear the path for the creation of drugs that can counter this graying effect. "Working out how our tissues change below stress is the first crucial step in direction of eventual treatment that can quit or revert the detrimental influence of stress".

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