#Gray hair is caused by stress — and is reversible: study

Relax — it could make your hair grow darker.

A new study published Tuesday in the journal eLife found that stress significantly influences when hair goes gray, but chilling out can reverse the trend. 

Researchers from Columbia University’s Vagelos College of Physicians and Surgeons reached these conclusions by analyzing the individual hairs of 14 volunteers in comparison to stress diaries each kept. 

The method they used is comparable to analyzing the rings of a tree: By looking at a tiny portion of each human hair, reflecting approximately an hour of hair growth, the scientists were able to find a correlation between times of stress and times of graying in the hair. 

Not only that, but they also found that periods of relaxation correlated with once-gray hair growing out dark. 

“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,” said associate professor of behavioral medicine and senior study author Martin Picard, Ph.D., in a press release. “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.”

The possibility of hair re-pigmentation is, the authors note, only selectively possible among certain age demographics. 

“Based on our mathematical modeling, we think hair needs to reach a threshold before it turns gray,” Picard said. “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.”

Additionally, hair that has already grown out of the follicle cannot change color — disproving the myth that Marie Antoinette’s hair went entirely gray the night before her 1793 beheading.