Picard was a co-author on the 2021 study published in the journal eLife that explored the role of stress in the advancement — and short-term reversal — of graying hair across a wide range of ages.

In the study, the researchers studied people who had strands of hair with darker pigment at either end but gray hair in the middle, and found that periods of stress reduction correlated with a temporary reversal of the graying process. In the case of one participant, taking a two-week vacation correlated with a repigmentation of hair.

 Why does hair turn gray?

However, unlike the infamous story of Marie Antoinette, whose hair supposedly went white overnight before her execution, it's important to remember that one or a handful of stressful days does not determine your hair color. Instead, Dr. Antonella Tosti, a professor of dermatology and cutaneous surgery at the University of Miami in Florida, told Live Science that environmental factors can be more impactful than individual stressful events.

"Oxidative stress, such as smoking or pollution, is something that definitely increases the risk of graying," Tosti said. Whether including antioxidants in your routine, such as antioxidant-rich foods like blueberries or pecans, can effectively combat these risks of gray hair specifically is still being determined, she said. But there is some evidence to support the idea that an antioxidant-rich diet can reduce effects of aging by helping reduce cell and DNA damage caused by unstable molecules called free radicals. Free radicals can occur naturally in the body and they can also be caused by external factors such as smoking, UV exposure and pollution.

Unfortunately, reducing personal and environmental stressors still won't entirely prevent hair from turning gray. More than half of people will begin going gray by the age of 50, and for individuals with a genetic lineage of early gray hair, genetics may play a bigger role than stress management, Dr. Joshua Zeichner, a dermatologist at Mount Sinai Hospital in New York City, told Live Science in an email.

"If you have a family history of early graying then you are likely to go gray early also," Zeichner said. "I have never seen gray hairs go back to normal, which may indicate that there is a permanent change to the hair follicle itself."

While there are no fully effective treatments or solutions to gray hair just yet, this doesn't mean that experts are giving up.

One potential path forward lies in what happens to melanocytes — a melanin-forming cell in the hair responsible for color — in gray hair. Scientists previously believed that melanocytes died off with age. But findings from a rat study published in the journal Nature in 2023 found that melanocytes may simply become concentrated at the follicle root of hair, no longer migrating up the strand to provide pigment.

Through medical treatments, there's a possibility that these melanocytes could be reactivated, Tosti said, to make the hair dark again. However, there's currently no process that can achieve this.

A treatment for oxidative stress may be another avenue, Zeichner said, by boosting free-radical fighting enzymes on the scalp through topical antioxidant application. But as for now, non-medical treatments at a local salon are probably the best bet at reducing grays.

"Right now, the only cure we have for gray hair is a good colorist," Zeichner said.

Story by Sarah Wells: Live Science