Scientists have finally figured out that long-term stress causes premature hair greying.
Age isn’t the only reason that your hair starts to go grey.
Our hair follicles contain melanocyte stem cells (MeSCs), which become active at the time of growth of new hair in the follicle. These cells convert into pigment making cells when new hair is made. Our body cannot replenish this pool of cells. Once they are damaged, the hair color vanishes.
How does stress cause premature greying of hair?
A 2013 study published in Nature Magazine found a link between long-term ongoing stress and hair color. As per researchers, hormones produced in response to stress can deplete the melanocyte stem cells leaving your hair grey or white.
Also, there is a bulk of literature supporting stress and the fight-or-flight response damaging the stem cells, which are very important for immunity. This explains why human beings feel sick after long periods of stress.
According to a 2020 study published in Nature, normal stress or fight-or-flight response activates the sympathetic nervous system. The system releases the neurotransmitter noradrenaline, or norepinephrine, which attacks the reservoir of melanocytes.
Hyperactivated sympathetic nerves trigger a rapid conversion of melanocytes into pigment-producing cells. This wipes out the supply of melanocyte stem cells from the niche and prevents the regeneration of hair pigment. The outcome is premature hair greying (see the image below).
In the study by Zhang et al., the research team found that blocking the release of noradrenaline from sympathetic neurons prevents stress-induced hair greying in their mice model.
Even without stress, if the sympathetic nervous system was overactivated, the mice’s hair turned grey. This partly explains why people with less stress in life are having grey hair in the mid-twenties and thirties.
What if an alternate mechanism makes your hair turn grey under stress?
Well, Zhang et al. did focus on this aspect. The research team examined if stress attacks the immune system and blocks the color-producing cells in the hair follicles.
They also analyzed if stress stimulates excess production of the stress hormone known as cortisol from adrenal glands causing hair color change.
So, they decided to experiment with mice lacking immune cells and adrenal glands. Mice were injected with a chemical – resiniferatoxin (a reliable method of mimicking stress response) to boost hormones like cortisol. But, that didn’t stop the rodent’s hair from turning grey or white.
It means under the stress – neither the weak immune system nor the release of cortisol from adrenal glands is responsible for turning your hair grey.
Upon further analysis, it was found that a part of the animals’ nervous system was depleting the hair pigment cells.
Together these results conclude that active sympathetic neurons releasing noradrenaline are causing the loss of melanocyte stem cells. Thus, speeding up the hair greying process.
How to reverse the premature greying of hair?
Zhang and colleagues’ work have well connected the dots between stress, fight or flight, stem-cell depletion and premature greying.
Although the dedicated team has decoded that stress makes hair turn grey, the exact mechanism is unclear.
However, it is yet to be determined if exactly the same mechanism causes premature aging because grey hair is associated with age. The research has widened the scope for future research and developing anti-greying therapies.