A team of researchers from Columbia University has carried out a study looking at what causes graying hair. The big news here: the team has found that, in some situations, it’s likely reversible. And while the study only enlisted 14 participants, its findings seem to coincide with common sense. Namely, that stressing about everything makes hair gray a lot faster than it otherwise would.

New Atlas reported on the study, which the team of researchers recently published in the journal eLife. The researchers, led by associate professor of behavioral medicine Martin Picard, claim this is the first study to offer quantitative evidence linking psychological stress to graying hair in people. (Researchers at Harvard performed a similar study in 2020, but on mice.)

“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 said in a press release. “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,” the associate professor added.

The researchers used a clever observation method to identify the source the participants’ graying hairs. Ayelet Rosenberg, first author of the study, created the method, which calls for capturing images of hair slices in extraordinary detail. Studying the slices, the researchers were able to quantify the extent of pigment loss in participants’ hair, a.k.a. graying. Each slice, incidentally, was only 1/20th a millimeter wide, and represented a single hour of growth.

Using this method, Picard and his team looked at the 14 participants’ hair in accordance with “stress diaries” they kept. The participants used the diaries—as their name implies—to keep track of when they were experiencing stress. And, indeed, the researchers found a correlation between stress and graying. So much so that one participant who went on vacation had five gray hairs revert back to dark.

An image of an eldery woman's graying hair.

romana klee

As for the biological impetus for the graying, the researchers peg stress’ effect on cells’ mitochondria as the culprit. Apparently, the “powerhouse” organelles respond poorly to psychological stress. And, as a result, fail to energize the cells that make up an individual’s hair follicles. But the researchers still call for people to curb their enthusiasm over the findings. Picard and his team say that while de-stressing can lead to de-graying, it’s unable to undo significant damage. Which is why even reborn Gandalf the Grey eventually became Gandalf the White, and not Gandalf the Jet Black