Harvard Scientists Discovered How Stress Turns Hair Gray

New York Times article in 2009 appeared with the headline, “After 44 days in the White House, Obama’s hair is grayer.” The article made waves as it referred to a usual trend of presidents’ hair turning significantly gray during their terms in the Whitehouse.

This idea of stress turning hair gray has spread through popular culture for centuries. It’s frequently referred to as Marie Antoinette syndrome, in indication to an oft-told, but a most likely fictional, story of the unlucky French queen’s hair turning white overnight after being caught during the revolution.

While the idea of one’s hair turning white immediately after an abrupt fright is an entertaining cartoonish fiction, there is a firm body of anecdotal evidence describing occasions where hair rapidly turns white after months, or even weeks, of trauma or stress.

“Everyone has a tale to share about how stress disturbs their body, particularly in their hair and skin – the only tissues we can see from the outside,” describes senior author on the new study, Ya-Chieh Hsu. “We wanted to understand if this association is true, and if so, how stress leads to alterations in diverse tissues. Hair pigmentation is such an available and tractable system to start with – and moreover, we were honestly curious to see if stress actually leads to hair graying.”

Prior to this new research, not only was it a secret as to how hair turns gray in times of stress, many scientists even asked whether stress could actually directly make hair go gray. It was generally believed that times of stress simply speeded up the aging process, and it was this mechanism that quickly turned hair gray.

In the initial stages of this new Harvard research, the team definitely may have suspected the prevailing consensus to be correct, but each early hypothesis rapidly led the researchers to dead ends. Was stress affecting immune cells to remove those pigment-producing cells in hair follicles? Nope, that wasn’t it. How about the well-researched stress hormone cortisol? Certainly, that must be playing a role in hair graying?

“Stress always raises levels of the hormone cortisol in the body, so we assumed that cortisol might play a role,” says Hsu. “But unexpectedly, when we separated the adrenal gland from the mice so that they couldn’t make cortisol-like hormones, yet their hair turned gray under stress.”

The first breakthrough arrived when the researchers found that when mice are stressed, their hair begins to turn gray due to a lessening in specific stem cells that are present at the base of hair follicles. These stem cells change into pigment-producing cells as hair grows but in times of immense stress, these stem cells are over-activated. This reduces the follicle’s reservoir of pigment-producing stem cells, causing the following hair growth to become gray.

“When we began to study this, I expected that stress was harmful to the body – but the damaging impact of stress that we discovered was more than what I imagined,” says Hsu. “After only a few days, all of the pigment-regenerating stem cells were gone. Once they’re lost, you can’t redevelop pigments anymore. The damage is lasting.”

But this finding didn’t explain precisely how stress was triggering these stem cells. It was shortly discovered that norepinephrine appeared to be triggering the excessive stem cell depletion. Though, taking away the animal’s primary source of norepinephrine, the adrenal gland, did not end the stress-induced graying.

The answer to this question is hidden in the body’s other main source of norepinephrine, the sympathetic nervous system (SNS), generally known as our fight-or-flight system.

The researchers learned that severe stress activates a release of norepinephrine from SNS neurons. This neurotransmitter consequently activates the mass migration of stem cells from the base of a hair follicle, and it is this progression that directly associates stress with hair graying.

“Severe stress, particularly the fight-or-flight response, has been traditionally regarded to be helpful for an animal’s survival,” clarifies Bing Zhang, lead author on the new study. “But in this situation, acute stress causes everlasting depletion of stem cells.”

It is vague at this stage whether the mechanism the Harvard team found is part of the natural process of age-related hair graying. Is this stress-induced graying only an accelerated version of what naturally happens to many people over numerous decades?

Christopher Deppman and Shayla Clark, two neuroscientists from the University of Virginia, wrote an editorial in the journal Nature, supplementing the publication of the new study. Calling the Harvard study “fascinating,” Clark and Deppman interestingly hypothesize what specific evolutionary function this type of stress-induced graying could serve.

“Because gray hair is most usually linked to age, it could be related to leadership, experience and trust,” the duo suggests. “For instance, adult, male, silverback mountain gorillas (Gorilla beringei beringei), which grow grey hair on their backs after gaining full maturity, can go on to direct a gorilla troop. Maybe an animal that has undergone enough stress to ‘earn’ grey hair has a top place in the social order than would normally be conferred by that individual’s age.”

Unconnected from these academic evolutionary considerations, the new research shines a persuasive light on how acute stress can play a direct part on the activity of stem cells. Determining this novel mechanism, of course, smooths the way for new methods that could inhibit hair graying, but even more fundamentally, the study opens the door to new ways to study the effects of stress on other structures in the body.

“By understanding specifically how stress affects stem cells that regenerate pigment, we’ve laid the foundation for understanding how stress affects other organs and tissues in the body,” settles Hsu. “Understanding how our tissues alter under stress is the first crucial step toward ultimate treatment inherently that can pause or revert the damaging impact of stress. Yet, we have a lot to learn in this zone.”

The new research was published in the journal Nature.


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