Legend has it that Marie Antoinette’s hair turned gray overnight just before her beheading in 1791.
Although the legend is inaccurate (hair that has already grown out of the follicle does not change color), a new study from researchers at Columbia University’s Vagelos College of Physicians and Surgeons is the first to offer quantitative evidence linking psychological stress. with gray hair in people.
And while it may seem intuitive that stress can accelerate aging, researchers were surprised to find that hair color can be restored when stress is removed, a finding that stands in contrast to a recent study in mice that suggested stress are permanent.
The study is of broader significance than confirming longstanding speculations about the effects of stress on hair color, says study lead author Martin Picard, associate professor of behavioral medicine at the Vagelos College of Physicians and Surgeons. Columbia University.
“Understanding the mechanisms that allow ‘old’ gray hair to revert to its ‘young’ pigmented states could provide new clues about the malleability of human aging in general and how it is influenced by stress,” says Picard.
“Our data adds to a growing body of evidence showing that human aging is not a fixed, linear biological process, but can, at least in part, be temporarily stopped or even reversed.”
Studying hair as a way to investigate aging
“Just as the rings in a tree trunk contain information about past decades in the life of a tree, our hair contains information about our biological history,” says Picard. “When the hairs are still under the skin as follicles, they are subject to the influence of stress hormones and other things that happen in our mind and body. Once the hairs grow out of the scalp, these exposures harden and permanently crystallize into a stable form. “
Although 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 accurately correlate times of stress with hair pigmentation at the level of a single follicle. .
Hair splitting to document hair pigmentation Ayelet Rosenberg, first author of the study and a student in Picard’s lab, developed a new method to capture highly detailed images of tiny slices of human hair to quantify the degree of pigment loss (graying) in each one of them. slices. Each slice, about 1/20 of a millimeter wide, represents about an hour of hair growth.
“If you use your eyes to look at a hair, it will appear to be the same color all over the body, unless there is a major transition,” says Picard. “Under a high-resolution scanner, you see small, subtle variations in color, and that’s what we are measuring.”
The researchers, whose study was published on June 22 on eLife, analyzed individual hairs of 14 volunteers. The results were compared to each volunteer’s stress diary, in which people were asked to review their calendars and rate the stress level for each week.
Researchers immediately noticed that some gray hair naturally reverts to its original color, which has never been quantitatively documented, Picard says.
When Shannon Rausser, second author of the paper and a student in Picard’s lab, aligned hair with stress diaries, striking associations were revealed between stress and graying of hair and, in some cases, a reversal of graying with lifting. of stress.
“There was one person who went on vacation, and five hairs on that person’s head went dark again during the vacation, synchronized in time,” says Picard.
Blame the connection between mind and mitochondria
To better understand how stress causes gray hair, the researchers also measured the levels of thousands of proteins in the hair and how the protein levels changed throughout each hair.
Changes in 300 proteins occurred when hair color changed, and the researchers developed a mathematical model that suggests that stress-induced changes in mitochondria may explain how stress turns hair gray.
“We often hear that mitochondria are the powerhouses of the cell, but that’s not the only role they play,” says Picard. “Mitochondria are actually like little antennae inside the cell that respond to a number of different signals, including psychological stress.”
The mitochondria connection between stress and hair color differs from that discovered in a recent study with mice, which found that stress-induced aging was caused by an irreversible loss of stem cells in the hair follicle.
“Our data show that aging is reversible in people, implying a different mechanism,” says co-author Ralf Paus, PhD, professor of dermatology at the University of Miami Miller School of Medicine. “Mice have very different hair follicle biology, and this may be a case where the findings in mice don’t translate well to people.”
Hair repigmentation is only possible for some
Reducing stress in your life is a good goal, but it won’t necessarily turn your hair into a normal color.
“Based on our mathematical model, we believe that hair must reach a threshold before it turns gray,” says Picard. “In middle age, when hair is near that threshold due to biological age and other factors, stress will push it over the threshold and it will turn gray.
“But we do not believe that reducing stress in a 70-year-old who has had gray hair for years will darken her hair or that increasing stress in a 10-year-old girl will be enough to tilt her hair above the gray threshold.”
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