Brazilian and American researchers have confirmed the popular belief that stress and anxiety cause grey hair. Their new study, carried out on mice, demonstrates the exact mechanisms of this intriguing phenomenon.
The idea that an emotionally traumatic event or period of intense stress can cause hair greying is widespread. "But so far, there has been little scientific validation of this link," stated the study’s authors in Nature. How does this bizarre hair discoloration happen?
To unravel this mystery, the study’s authors conducted experiments on laboratory mice. The mice were exposed to distinct stressors. Each stress factor led to the appearance of white or grey hairs on the animals.
A neurotransmitter is the culprit
The researchers then turned their focus to melanocyte (pigment-producing) stem cells located at the base of the hair follicles, the space from which hair grows. These cells are linked with neurons from the sympathetic nervous system. The neurons release the neurotransmitter norepinephrine during moments of stress or fear. Once this system has been activated, the neurotransmitter acts on the melanocyte stem cells responsible for hair color.
Normally, these stem cells stay dormant until a new hair is being produced. Once the store of melanocyte stem cells has run out, creation of pigment in the follicle bulbs is no longer possible. As a result, hairs produced by the follicle will be permanently white.
In order to verify their hypothesis and attempt to counter these effects, the researchers administered a treatment for high blood pressure in order to block the action of norepinephrine, which prevented the appearance of grey or white hairs on the mice.
"With this study, we now know that neurons can control stem cells and their function, and can explain how they interact at the cellular and molecular level to link stress with hair graying. 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," stated the researchers.