A scientific study has confirmed the widespread perception that stress can turn a person’s hair grey.
In experiments on mice, stem cells that control skin and hair colour became damaged after intense stress. It was found that dark furred mice turned completely white within weeks.
Men and women can start to go grey from any point around their mid 30s, timings usually depend on genetics or can be a consequence of some nutritional diseases or disorders.
Ageing is perceived as the main reason behind the production of grey hair, but new research published in the journal, Nature, has found that stress can also contribute to its appearance.
Why does hair turn grey?
Hair colour is determined by cells called melanocytes, which produce melanin and come from a specific type of stem cells that are located in the hair follicle.
As a person ages, melanocyte stem cells become depleted, resulting in a progressive loss of pigments - meaning hair turns grey.
Though the greying process is primarily a result of ageing, stress can also play a part in this process.
Since stress affects the whole body, researchers were keen to establish what specific mechanism linked stress with the pigmentation of hair.
It is not an autoimmune or cortisol response
The first hypothesis was that stress causes an autoimmune attack in pigment producing cells. However, in a trial with mice that lacked immune system cells, the scientists observed no differences with respect to the other group. The team also found no link between pigmentation changes and the release of cortisol.
Harvard researcher Chieh Hsu explained: “Stress always elevates levels of the hormone cortisol in the body, so we thought that cortisol might play a role. Though, surprisingly, when we removed the adrenal gland from the mice so that they couldn’t produce cortisol-like hormones, their hair still turned grey under stress.”
The key is norepinephrine
The researchers found that the activation of the sympathetic nervous system, involved in automatic responses to stress, seems to enhance the loss of melanocyte stem cells that leads to the appearance of grey hair.
These cells have specific receptors for norepinephrine, which is another of the neurotransmitters involved in the ‘fight or flight’ response associated with stress or danger.
When scientists blocked these receptors for norepinephrine, grey hair stopped appearing as a result of stress. In addition, the results revealed that the areas with more sympathetic innervation were more prone to greying.
“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 pigments anymore. The damage is permanent.”
The evolutionary advantages of having white hair
As Shayla A. Clark and Christopher D. Deppmann explain in a review of the article published by Nature, grey hair could be associated with greater experience and leadership.
For example, the back of the male mountain gorilla is covered with grey hair when they reach adulthood. It is only at this ‘greying’ point that they are able to occupy the top spot in their hierarchy band.
Applications beyond anti-grey therapies
“We know that peripheral neurons powerfully regulate organ function, blood vessels, and immunity, but less is known about how they regulate stem cells,” Chiu said.
“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 levels to link stress with hair greying.”
Many could hope that these findings could lead to the development of a treatment to delay the appearance of grey hair, but that is something that will not happen in the near future.
This research does mark provide a baseline to further explore how stress affects other organs and how to block its most harmful effects on health.
Reference: Zhang et al. 2020. Hyperactivation of sympathetic nerves drives depletion of melanocyte stem cells. Nature doi.org/10.1038/s41586-020-1935-3