The next time you tell your rebellious teenagers that their antics are giving you gray hair, know that the latest animal research seems to confirm your claim.
Scientists report they have pinpointed how stress causes gray hair in mice, and they said that their findings improve knowledge of how stress can affect the human body.
"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," said study senior author Ya-Chieh Hsu, an associate professor of stem cell and regenerative biology at Harvard University.
"We wanted to understand if this connection is true and, if so, how stress leads to changes in diverse tissues," Hsu said in a Harvard news release. "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."
In research with mice, Hsu and her colleagues found that stress activates nerves that are part of the fight-or-flight response, resulting in permanent damage to pigment-regenerating stem cells in hair follicles.
"When we started to study this, I expected that stress was bad for the body -- but the detrimental impact of stress that we discovered was beyond what I imagined," Hsu said. "After just a few days, all of the pigment-regenerating stem cells were lost. Once they're gone, you can't regenerate pigment anymore. The damage is permanent."
The finding, which may not pan out in humans, highlights the negative side effects of the fight-or-flight response, the researchers said.
The team published its report Jan. 22 in the journal Nature.
According to study lead author Bing Zhang, a postdoctoral fellow at Harvard, "Acute stress, particularly the fight-or-flight response, has been traditionally viewed to be beneficial for an animal's survival. But in this case, acute stress causes permanent depletion of stem cells."
Hsu added that, "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."
Therefore, "understanding how our tissues change under stress is the first critical step towards eventual treatment that can halt or revert the detrimental impact of stress," she said. "We still have a lot to learn in this area."
The U.S. National Institute of Mental Health has more on stress.