But it's reversible, researchers find
Columbia
University Irving Medical Center
Though 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 Vagelos
College of Physicians and Surgeons is the first to offer quantitative evidence
linking psychological stress to graying hair in people.
And while it may
seem intuitive that stress can accelerate graying, the researchers were
surprised to discover that hair color can be restored when stress is
eliminated, a finding that contrasts with a recent study in mice that suggested
that stressed-induced gray hairs are permanent.
The study, published June 22 in eLife, has broader significance than confirming age-old speculation about the effects of stress on hair color, says the study's senior author Martin Picard, PhD(link is external and opens in a new window), associate professor of behavioral medicine (in psychiatry and neurology) 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," Picard says.
"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."
Studying hair as an avenue to investigate aging
"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," Picard
says. "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."
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.
Splitting hairs
to document hair pigmentation Ayelet Rosenberg, first author on the study and a
student in Picard's laboratory, developed a new method for capturing highly
detailed images of tiny slices of human hairs to quantify the extent of pigment
loss (graying) in each of those slices. Each slice, about 1/20th of a
millimeter wide, represents about an hour of hair growth.
"If you use
your eyes to look at a hair, it will seem like it's the same color throughout
unless there is a major transition," Picard says. "Under a
high-resolution scanner, you see small, subtle variations in color, and that's
what we're measuring."
The researchers
analyzed 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 regain their
original color, which had never been quantitatively documented, Picard says.
When hairs were
aligned with stress diaries by Shannon Rausser, second author on the paper and
a student in Picard's laboratory, striking associations between stress and hair
graying were revealed and, in some cases, a reversal of graying with the
lifting of stress.
"There was
one individual who went on vacation, and five hairs on that person's head
reverted back to dark during the vacation, synchronized in time," Picard
says.
Blame the mind-mitochondria connection
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.
Changes in 300
proteins occurred when hair color changed, and the researchers developed a
mathematical model that suggests stress-induced changes in mitochondria may
explain how stress turns hair gray.
"We often
hear that the mitochondria are the powerhouses of the cell, but that's not the
only role they play," Picard says. "Mitochondria are actually like
little antennas 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 of mice, which found that stress-induced graying was caused by an
irreversible loss of stem cells in the hair follicle.
"Our data
show that graying is reversible in people, which implicates 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 an instance where findings in mice don't
translate well to people."
Hair re-pigmentation only possible for some
Reducing stress
in your life is a good goal, but it won't necessarily turn your hair to a
normal color.
"Based on
our mathematical modeling, we think hair needs to reach a threshold before it
turns gray," Picard says. "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 gray.
"But we
don't think that reducing stress in a 70-year-old who's been gray for years
will darken their hair or increasing stress in a 10-year-old will be enough to
tip their hair over the gray threshold."
More information
The study is
titled "Quantitative Mapping of Human Hair Greying and Reversal in
Relation to Life Stress."
All contributors
(all from Columbia unless noted): Ayelet Rosenberg, Shannon Rausser, Junting
Ren, Eugene V. Mosharov, Gabriel Sturm, R. Todd Ogden, Purvi Patel, Rajesh
Kumar Soni, Clay Lacefield (New York State Psychiatric Institute), Desmond J.
Tobin (University College Dublin), Ralf Paus (University of Miami, University
of Manchester, UK, and Monasterium Laboratory, Münster, Germany), and Martin
Picard.
The research was
funded by grants from the Wharton Fund and the National Institutes of Health
(grants GM119793, MH119336, and AG066828).
