Scientists from Harvard University have proven the well established myth that stress can turn hair grey.
In the study on mice, researchers found that stress activates nerves that are part of the fight-or-flight response, which can cause permanent damage to 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,” said Senior Author Ya-Chieh Hsu.
“We wanted to understand if this connection is true, and if so, how stress leads to changes in diverse tissues.
“Hair pigmentation is such an accessible and tractable system to start with and we were genuinely curious to see if stress indeed leads to hair greying.”
The team were able to discover the link by systematically eliminating different body systems to find which was responsible for connecting stress to hair colour.
“Stress always elevates levels of the hormone cortisol in the body, so we thought that cortisol might play a role,” said Hsu.
Eventually, the sympathetic nerve system, which is responsible for the body’s fight-or-flight response, was tested.
The nerves were found to branch out into each hair follicle on the skin, and stress caused these nerves to release norepinephrine, a stress hormone and neurotransmitter, which is taken up by nearby pigment-regenerating stem cells.
Norepinephrine causes the stem cells to activate excessively and convert into pigment-producing cells, prematurely depleting the reservoir.
“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.
“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.”
