Fact or Fiction?: Stress Causes Gray Hair
Oct 2007
While no clear link has been found, scientists believe
that stress can lead to more gray in your hair.
Legend has it that Marie Antoinette's hair turned white
the night before she was guillotined. Presumably the
stress of impending decapitation caused her locks to
lose color within hours. Extremely unlikely, scientists
say, but stress may play a role in a more gradual
graying process.
The first silvery strands usually pop up around age 30
for men and age 35 for women, but graying can begin as
early as high school for some and as late as the 50s for
others.
Graying begins inside the sunken pits in the scalp
called follicles. A typical human head has about 100,000
of these teardrop-shaped cavities, each capable of
sprouting several hairs in a lifetime.
At the bottom of each follicle
is a hair-growing factory where cells work together to
assemble colored hair. Keratinocytes (epidermal cells)
build the hair from the bottom up, stacking atop one
another and eventually dying, leaving behind mostly
keratin, a colorless protein that gives hair its texture
and strength. (Keratin is also a primary component of
nails, the outer layer of skin, animal hooves and
claws?even rhinoceros horns.)
As keratinocytes construct hairs, neighboring
melanocytes manufacture a pigment called melanin, which
is delivered to the keratinocytes in little packages
called melanosomes.
Hair melanin comes in two shades—eumelanin (dark brown
or black) and pheomelanin (yellow or red)—that combine
in different proportions to create a vast array of human
hair colors. Hair that has lost most of its melanin is
gray; hair that has lost all of this pigment is white.
At any given time, around 80 to 90 percent of the hairs
on a person's head are in an active growth phase, which
may last anywhere from two to seven years.
At the end of this stage, the
follicle shrivels, the keratinocytes and melanocytes
undergo programmed cell death (apoptosis), and the
follicle enters a resting phase, during which the hair
falls out.
To begin building a new hair, the follicle factory must
be rebuilt. Fresh keratinocytes and melanocytes are
recruited from progenitor cells, also called "stem
cells," residing at the bottom of the follicle.
For unknown reasons,
keratinocyte stem cells have a much greater longevity
than the melanocyte stem cells, says David Fisher,
professor of pediatrics at Harvard Medical School. "It's
the gradual depletion of [melanocyte] stem cells that
leads to the loss of pigment," he says.
Does stress accelerate this demise of the melanocyte
population? "It is not so simple," Fisher says, noting
that the process of graying is a multivariable equation.
Stress hormones may impact the survival and / or
activity of melanocytes, but no clear link has been
found between stress and gray hair.
Suspicions—and hypotheses—abound, however. "Graying
could be a result of chronic free radical damage," says
Ralf Paus, professor of dermatology at the University
Hospital Schleswig-Holstein in Lübeck, Germany.
Stress hormones produced either
systemically or locally (by cells in the follicle) could
produce inflammation that drives the production of free
radicals—unstable molecules that damage cells—and "it is
possible that these free radicals could influence
melanin production or induce bleaching of melanin," Paus
says.
"There is evidence that local expression of stress
hormones mediate the signals instructing melanocytes to
deliver melanin to keratinocytes," notes Jennifer Lin, a
dermatologist who conducts molecular biology research at
the Dana-Farber / Harvard Cancer Center in Boston.
"Conceivably, if that signal is disrupted, melanin will
not deliver pigment to your hair."
And general practice physicians have observed
accelerated graying among patients under stress, says
Tyler Cymet, head of family medicine at Sinai Hospital
in Baltimore, who conducted a small retrospective study
on hair graying among patients at Sinai. "We've seen
that people who are stressed two to three years report
that they turn gray sooner," he says.
