The real reason hair goes grey? Because stress touches a nerve

WHEN the French queen Marie Antoinette was seized during the French Revolution in 1793, her hair reportedly turned white overnight.

Now, scientists have established that extreme stress really can make hair go grey, by turning off the pigment-regenerating stem cells that provide colour.

“Everyone has an anecdote to share about how stress affects their body, particularly in their skin and hair, the only tissues we can see from the outside,” said Ya-chieh Hsu, the senior author of the study, and associate professor of stem cell and regenerative biology at Harvard University.

“We wanted to understand if this connection is true and, if so, how stress leads to changes in diverse tissues. We were genuinely curious to see if stress indeed leads to hair greying.”

Scientists initially thought the immune system might be responsible, going haywire during extreme stress and attacking the pigment cells. But the effect still happened in tests on mice, which do not have immune systems.

They then looked at whether the stress hormone cortisol might be causing damage, but the mice’s hair went grey even after the removal of their adrenal gland, which produces cortisol.

After systematically eliminating different possibilities, researchers homed in on the sympathetic nerve system, responsible for the body’s fight-or-flight response.

The researchers found that stress causes sympathetic nerves to release the chemical norepinephrine, which gets taken up by nearby pigment-regenerating stem cells.

The chemical caused stem cells to become excessively active, sending them into overload and depleting their colour reservoir.

“After just a few days, all of the pigment-regenerating stem cells were lost. Once they’re gone, you can’t regenerate pigment anymore,” said Dr Hsu. “The damage is permanent.”

Although fight-or flight is generally a beneficial response, it also shuts down many systems the body does not deem beneficial to survival. Most of those systems come back, but the study shows some can be damaged permanently.

Researchers hope the findings can help illuminate the broader effects of stress on various organs and tissues, and pave the way for drugs that can stop the damaging impact.

The study was published in the journal Nature.