The phenomenon of hair turning white from fright, shock, grief, or trauma persists in literature, Hollywood, and a new study from Harvard University.
Research published in the journal Nature explains how stress can trigger follicular color change.
A team of Harvard scientists found that activating humans’ fight-or-flight response can permanently damage pigment-regenerating stem cells in hair follicles.
“Everyone has an anecdote to share about how stress affects their body, particularly in their skin and hair—the only tissues we can see from the outside,” according to senior study author and biology professor Ya-Chieh Hsu.
(I am convinced that my husband had a lot fewer grays when we started dating five years ago…)
“We wanted to understand if this connection is true, and if so, how stress leads to changes in diverse tissues,” Hsu continued. “Hair pigmentation is such an accessible and tractable system to start with—and besides, we were genuinely curious to see if stress indeed leads to hair graying.”
Stress affects the whole body, so researchers had to narrow down which specific systems are involved. With some trial and error, they ruled out the immune system and cortisol hormone, among other possibilities.
The team finally settled on the sympathetic nervous system, responsible for our fight-or-flight response.
Ya-Chieh Hsu shows off a diagram of a hair follicle (via Jon Chase/Harvard University)
Sympathetic nerves branch out into each hair follicle on the skin; when stressed, those nerves release norepinephrine, which gets absorbed by nearby pigment-regenerating stem cells.
Those cells get knocked into overdrive, each one producing pigment to color the hair and prematurely depleting the reservoir.
“Once they’re gone, you can’t regenerate pigments anymore,” Hsu said. “The damage is permanent.”
“When we started to study this, I expected that stress was bad for the body,” she added, “but the detrimental impact of stress that we discovered was beyond what I imagined.”
These findings highlight the negative effects of what is otherwise a beneficial evolutionary trait: the fight-or-flight response.
“By understanding precisely how stress affects stem cells that regenerate pigment, we’ve laid the groundwork for understanding how stress affects other tissues and organs in the body,” Hsu said.
This is the “first critical step” toward treatment that may eventually halt or reverse the detrimental results of stress.
“We still have a lot to learn in this area,” Hsu admitted.
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