It’s no secret that stress causes white hair to appear. If the correlation between the two has been presumed for years, it has never been explained. For the first time, a study has just revealed why stress is an important factor in the arrival of white hair.
We dread all their appearances. White hair is often associated with old age. However, age is not the only culprit. Stress also has a role to play. And it is now proven, stress does indeed accelerate the appearance of white hair, according to a study carried out by a team of researchers from the Research Center of Inflammatory Diseases (CRID) of Sao Paulo and Harvard University , published this January 22 in the scientific journal Nature .
“Everyone has an anecdote to share about how stress affects their bodies, especially their skin and hair, the only tissue we can see from the outside,” said lead author Ya. -Chieh Hsu. “We wanted to understand if this link is true, and if so, how stress causes changes in various tissues. Hair pigmentation is such an accessible and easy-to-master system at the outset and moreover, we were really curious to see if stress actually leads to graying of hair. “
Tests performed on mice
To draw this conclusion, the researchers tested different types of stress, including pain , restriction and unpredictability, on dark-haired mice to easily identify possible white hairs. Scientists first assumed that stress could cause an immune attack on the stem cells that control the pigments in the skin and hair. However, the hairs of the mice still turned white when they lacked immune cells.
The researchers then turned to cortisol , the stress hormone. “Stress always increases cortisol levels in the body, so we thought cortisol could play a role,” said Hsu. “But surprisingly, when we removed the adrenal gland from the mice so that they couldn’t produce cortisol-type hormones, their hair turned gray under stress.”
A link between the nervous system and stem cells
After eliminating the various possibilities, the scientists discovered a link between the nervous system and stem cells. The team found that stress activates the nerves involved in the “fight or flight response” . These nerves, in turn, will cause permanent damage and depletion of the stem cells that regenerate the pigments in the hair follicles (the cavity in which the hair takes birth).
The scientists then concluded that stress triggers nerves to release norepinephrine, a precursor to adrenaline, which is absorbed by regenerative pigment stem cells. Noradrenaline causes excessive activation of stem cells. When the hair regenerates, some stem cells all transform into cells that produce pigments that color the hair.
“After only a few days, all the pigment regenerating stem cells have been lost. Once they are gone, the pigment can no longer be regenerated. The damage is permanent,” said Hsu. “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 to graying of hair . “