My first gray hair appeared when I was the age of twenty-three, within two months of my mom passing away. Of course, this is anecdotal evidence and should not be taken as proof that stress causes hair to go gray. However, as it turns out, science agrees with my anecdote, and research has repeatedly shown that hair (or fur in non-human animals) can turn gray due to high stress levels.
In a study published in Nature in 2020, researchers exposed black-colored mice to stress via a few different mechanisms, including restraining them, tilting their cages, rapidly changing their lighting on and off at unpredictable times or leaving them on all night, supplying them damp bedding, or injecting them with resiniferatoxin, a capsaicin analog (capsaicin is the active ingredient in chili peppers). After experiencing these stressors, mice developed more white fur.
The scientists investigated further and determined that stress led to the activation of the sympathetic nerves running to the hair follicle, causing a release of norepinephrine (also called noradrenaline). Hair color is due to pigment cells called melanocytes, which are made from melanocyte stem cells. The rapid influx of norepinephrine causes a greater number than usual of melanocyte stem cells to begin becoming “grown-up” melanocytes. When they migrate out of the hair follicle, or grow up and move out, if you will, the follicle never recovers its ability to generate pigment cells, and from then on produces an unpigmented, a.k.a. gray or white, hair.
Just over a year later, another study was published in eLife that also supported the graying effects of stress but challenged the permanent nature of the change. These researchers likened hairs to trees and developed a method for looking at tiny slices of human hairs and correlating their condition to the stress of the owner’s life, just as we can look at the rings in a tree to infer its history. The scientists looked at slices roughly 1/20th of a millimeter wide, representing about one hour of hair growth. Analyzing hairs from fourteen volunteers and correlating what they saw with their stress diaries showed that while some gray definitely followed stressful times, some hairs regained their pigment when stress abated.
So yes, stress can absolutely cause gray hair. But pigment change in our luscious locks isn’t as black or white as it seems, and taking some time to destress after an anxious period in your life could benefit you in many ways.