Scientifically Speaking | Yes, it’s true, stress turns hair grey - Hindustan Times

Scientifically Speaking | Yes, it’s true, stress turns hair grey

ByAnirban Mahapatra
Aug 16, 2023 09:25 AM IST

Hearteningly, recent studies have shown, it can be reversed as well. Re-pigmentation occurred when there was a decrease in stress. But there’s a caveat

The passage of time is narrated on our bodies through the wrinkles in our skin and the greying of our hair. Grey hair is also a sign of wisdom. It’s known that genetics plays a part in determining at what age someone’s hair will turn grey. After all, premature greying tends to run in families. It’s also widely believed that stress can hasten the greying of hair. The darker hair of American Presidents, when they assumed office compared to when they left, has been attributed to the demanding nature of the office.

Until recently there was little scientific evidence explaining the role of stress in greying hair.(Stock) PREMIUM
Until recently there was little scientific evidence explaining the role of stress in greying hair.(Stock)

There’s an apocryphal story that the French Queen, Marie Antoinette’s hair turned white the night before her execution by guillotine at the age of 37. While this anecdote is likely untrue, it feeds into our belief that stress and fear can turn hair grey.

Popular wisdom aside, until recently there was little scientific evidence explaining the role of stress in greying hair. A pioneering study from Harvard University published in the prestigious scientific journal Nature in 2020 provided the first solid backing for stress-induced greying. A seminal study from Columbia University in eLife, an open access scientific journal, the following year, built on this study and found that in certain cases greying of hair is reversible.

Not so black and white

To set the stage for understanding these studies, we need to first examine the life cycle of hair. Hair is an extension of tiny hair follicles embedded in the skin. These follicles determine the life cycle of hair which is composed of periods of active growth (anagen), regression (catagen), and rest (telogen). Depending on the location of the hair on the body, these cycles can last from a few months to several years. Hair colour is derived from the pigment, melanin, which is produced by cells known as melanocytes during the anagen phase.

Melanocytes originate from melanocyte stem cells within the hair follicle. As we get older, these stem cells gradually diminish, leading to loss of hair colour and hence grey hair.

In 2020, researchers at Harvard University found the link between stress and accelerated hair greying. The team turned to mice to see if stress could lead to greying. Indeed, it did. While mice aren’t perfect substitutes for humans, they serve as useful proxies in laboratory experiments. You can subject laboratory mice to stress, observe them in closed settings, and dissect them to elucidate mechanisms of biological processes such as hair greying.

Like detectives, the team narrowed the list of possible causes of stress-induced hair greying through the process of elimination. They ruled out the possibility of an immune attack on pigment cells and the stress hormone cortisol as the culprit.

Instead, it turns out that the offender was the sympathetic nerve system.

The network of sympathetic nerves reaches every hair follicle. It becomes activated during times of stress and releases the chemical norepinephrine. Melanocyte stem cells take up this released chemical. This causes them to proliferate rapidly, differentiate into melanocytes, and then move away from the hair follicles. This burst of activity exhausts reserves, leading to loss of pigment and grey hair.

The grey zone

Greying of hair isn’t always permanent in people though. In 2021, researchers at Columbia University found that under certain conditions, grey hair can return to its original colour. Reducing stress can reverse the process.

The team developed a way to digitally track hair pigment patterns along the length of a single hair with greater precision. Then they matched changes in hair pigmentation to specific times. This allowed them to map changes in hair colour to stressful life events.

Have you ever seen one of your hairs turn grey and then grow out to its original colour again? The team reported such a process of repigmentation of hair in 14 people.

What’s most important is that because they could map the time of greying, they could see that re-pigmentation occurred when individuals reported a decrease in stress. This was the first time this had been reported in the scientific literature. The team concluded that hair turning grey and regaining pigment was a biological process that happened within a single anagen phase.

Building on these findings, the team developed a mathematical model to simulate the greying process over time, accounting for factors such as ageing and stress. This model is useful because stress at different ages might have different effects.

So, is stress-related greying hair permanent or reversible? The answer is that it is both. It really depends on the context. As Martin Picard, the senior author of the eLife study notes, “In middle age, when the hair is near that threshold because of biological age and other factors, stress will push it over the threshold, and it transitions to grey. But we don’t think that reducing stress in a 70-year-old who’s been grey for years will darken their hair or increasing stress in a 10-year-old will be enough to tip their hair over the grey threshold.”

Anirban Mahapatra is a scientist by training and the author of a popular science book on COVID-19. The views expressed are personal.

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