Scientists have proven that extreme stress really can make the hair turn grey, by turning-off the pigment-regenerating stem cells which colour follicles.

Axar.az reports citing foreign media:

“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 senior author Ya-Chieh Hsu, an 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 graying.”

Scientists initially thought the immune system might be responsible, going haywire during extreme stress and attacking the pigment cells. But in mice without immune systems the effect still happened.

They then looked at whether the stress hormone cortisol might be causing damage, but after removing the adrenal gland from mice, they found their hair still went grey.

After systematically eliminating different possibilities, they honed in on the sympathetic nerve system, which is responsible for the body's fight-or-flight response.

Sympathetic nerves branch out into each hair follicle on the skin. The researchers found that stress causes these nerves to release the chemical norepinephrine, which gets taken up by nearby pigment-regenerating stem cells.

Researchers found that the norepinephrine from sympathetic nerves causes the stem cells to activate excessively, sending them into overload and depleting the colour reservoir.