A new study carried out by researchers at the Columbia University Vagelos College of Physicians and Surgeons, United States, has revealed how psychological stress causes grey hair.
According to the researchers, while stress can accelerate graying, the hair colour can still be restored when stress is eliminated.
Their finding contrasts with a recent study in mice that suggested that stressed-induced gray hairs are permanent.
The study, published in ScienceDaily, has broader significance than confirming age-old speculation about the effects of stress on hair colour, says the study’s senior author Dr. Martin Picard, an associate professor of behavioral medicine at Columbia University Vagelos College of Physicians and Surgeons.
“Understanding the mechanisms that allow ‘old’ gray hairs to return to their ‘young’ pigmented states could yield new clues about the malleability of human aging in general and how it is influenced by stress.
“Our data add to a growing body of evidence demonstrating that human aging is not a linear, fixed biological process but may, at least in part, be halted or even temporarily reversed.
“Just as the rings in a tree trunk hold information about past decades in the life of a tree, our hair contains information about our biological history.
“When hairs are still under the skin as follicles, they are subject to the influence of stress hormones and other things happening in our mind and body. Once hairs grow out of the scalp, they harden and permanently crystallize these exposures into a stable form”, Picard says.
Though people have long believed that psychological stress can accelerate gray hair, scientists have debated the connection due to the lack of sensitive methods that can precisely correlate times of stress with hair pigmentation at a single-follicle level.
The researchers analysed individual hairs from 14 volunteers. The results were compared with each volunteer’s stress diary, in which individuals were asked to review their calendars and rate each week’s level of stress.
“The investigators immediately noticed that some gray hairs naturally regained their original colour, which had never been quantitatively documented. If you use your eyes to look at a hair, it will seem like it’s the same colour throughout unless there is a major transition. Under a high-resolution scanner, you see small, subtle variations in colour, and that’s what we’re measuring”, Picard added.
Co-author of the study and professor of dermatology at the University of Miami Miller School of Medicine, Ralf Paus, said “Our data show that graying is reversible in people, which implicates a different mechanism.
“Mice have very different hair follicle biology, and this may be an instance where findings in mice don’t translate well to people.”
To better understand how stress causes gray hair, the researchers also measured levels of thousands of proteins in the hairs and how protein levels changed over the length of each hair.
US and Brazilian researchers had in a recent study on mice said stem cells that control skin and hair colour became damaged after intense stress.
But scientists were not clear exactly how stress affected the hairs on our heads.
Men and women can go grey any time from their mid-30s, with the timing of parental hair colour change giving most of the clues on when.
Although it’s mostly down to the natural ageing process and genes, stress can also play a role.
“We now know for sure that stress is responsible for this specific change to your skin and hair, and how it works,” says Prof Ya-Cieh Hsu, research author from Harvard University.
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