• Robb G. Best

Stress-Induced Gray Hairs May Be Reversible

At some point, you've probably heard someone joke about how a stressful event is turning their hair gray. You probably took this in as a figurative statement. The person who said it probably intended it that way, too. However, new studies show that stress can indeed turn one's hair gray--and even more interestingly, undoing the causes of that stress can sometimes also restore the hair color.

A new study from Columbia University Vagelos College of Physicians and Surgeons is the first to prove the "you're giving me gray hairs!" wive's tale. And in contrast to a recent mouse study, those gray hairs seem to not always be permanent.

Martin Picard, PhD, associate professor of behavioral medicine (in psychiatry and neurology) is the study's lead author. Says Picard, “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."

The state of one's hair can hold a remarkably good record of what a person has been through, Picard explains. “When hairs are still under the skin as follicles, they are subject to the influence of stress hormones and other things happening in our mind and body. Once hairs grow out of the scalp, they harden and permanently crystallize these exposures into a stable form.”

The trouble is, you need to really be able to look at the hair. Accordingly, study first author and student of Picard Ayelet Rosenberg developed a new method of capturing extremely detailed images of tiny slices of human hair, in order to measure the degree of graying in each sample. One 1/20 millimeter-wide slice records about an hour's worth of hair growth.

Picard says that while a casual, unaided glance at a strand of hair will generally give you the impression of a single color, in reality, there are subtle variations all through the strand. The team studied these variations using samples from 14 volunteers. The volunteers also kept stress diaries, in which they looked over their calendars and rated each week for stress.

Shannon Rausser, another one of Picard's students and second author of the paper, compared the hair samples against the diaries to discover direct associations between stress and levels of gray. Rausser also found that in some cases, when the stress lifted, hair color reversed away from graying. “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,” Picard reports.

What gives? For a more complete picture of the science behind this phenomenon, the researchers also looked at protein variations across the hair strands. When hair shifted gray, it represented changes in roughly 300 proteins. The researchers created a mathematical model which suggested that the mechanism that turns hair gray be be linked to stress reactions in the mitochondria. These mitochondria exist within the cell, and respond to a variety of signals, including stress levels.

This connection, between the mitochondria, stress, and hair color, was first found in mice. However, there, the graying was caused by a loss of stem cells in the hair follicle--a permanent change. This difference suggests that mouse hair aging operates on a separate mechanism, notes co-author Ralf Paus, PhD, professor of dermatology at the University of Miami Miller School of Medicine. He adds, “Mice have very different hair follicle biology, and this may be an instance where findings in mice don’t translate well to people.”

Still, it is important not to take these test results too far. Lowering your stress levels is generally a good idea but you can't indefinitely force all your hair back to its original color just by booking infinite vacations. Picard notes that there is a certain threshold hair reaches before it turns gray. Stress is a factor, but so are biological age and other variables. Stress can simply sometimes provide that last little shove--or not--over the threshold.

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