Does Stress Cause Gray Hair? What the Research Shows

Stress can speed up graying, according to a 2020 study in mice and a 2021 study of human hairs. In the mice, a burst of stress signals from nerves used up the stem cells that make new pigment cells, and the change was permanent. In people, some hairs went gray during stressful periods and a few regained color when stress eased, but that study included only 14 people.

An old belief, recently tested

The link between stress and gray hair is a common belief. The authors of the 2021 study describe graying as a sign of aging that is "generally believed to be irreversible and linked to psychological stress." Until recently, though, there was little direct evidence. The plain-language summary of their paper notes that research in mice suggested stress may speed up graying, but that there was no definitive research on this in humans.

The American Academy of Dermatology (AAD) now states that stress has been shown to speed up signs of aging, including gray hair. Two studies tested the link directly.

The 2020 mouse study

A team at Harvard University, led by Ya-Chieh Hsu, published the first of these two studies in Nature in 2020. They worked with black-haired mice and used three kinds of stress:

• Restraint: limiting the mice's movement for periods of time.
• Chronic unpredictable stress: a changing series of mild stresses over time.
• Pain: an injection of resiniferatoxin, a chemical that triggers pain signals.

All three turned hair gray. With restraint and chronic unpredictable stress, the graying became clear after 3 to 5 rounds of hair growth. The pain injection had the fastest and strongest effect. Many of the new hairs in the next growth cycle had no pigment. Within 5 days of the injection, the number of pigment stem cells had dropped sharply. In all three conditions, the loss of pigment was permanent.

Hsu told the Harvard Gazette that "the detrimental impact of stress that we discovered was beyond what I imagined."

How stress used up the stem cells

The team first suspected the immune system. But mice without immune cells still turned gray. They then tested stress hormones such as cortisol, which comes from the adrenal glands. Mice with their adrenal glands removed still turned gray, and raising the mouse version of cortisol through food did not change the stem cells or the hair color.

In the mice, the cause was the sympathetic nervous system. This is the set of nerves that drives the body's fast reaction to danger, often called fight or flight. These nerves reach the area of the follicle where the pigment stem cells rest. Under stress, the nerves released a burst of norepinephrine, a chemical messenger. The stem cells, which normally stay quiet, began to multiply quickly. They turned into pigment cells, moved away and were gone for good.

The team confirmed this in several ways:

• Cutting off the sympathetic nerves, or blocking their release of norepinephrine with a drug called guanethidine, prevented the graying.
• Removing the norepinephrine receptor from the stem cells stopped white hairs from forming.
• Drugs that pause cell division kept the stem cells resting, and they stayed in place.

In lab dishes, human pigment cells also switched on genes for cell division after exposure to norepinephrine. The main experiments, however, were all in mice. Our page on how hair gets its color explains what these stem cells normally do.

The 2021 study of human hairs

The second study came from Columbia University. It was led by Martin Picard and published in eLife in 2021. The team developed a way to measure color along a single hair in very fine detail. A hair grows from the root, so its length holds a record of recent months. According to Columbia, each slice they measured was about 1/20 of a millimeter wide and stood for about an hour of growth.

The volunteers were 14 people, seven women and seven men, aged 9 to 65. The team studied 397 hairs from the scalp and other parts of the body. Each volunteer also looked back over their calendar and rated the stress of each week. The researchers then compared the stress ratings with the color changes along each hair.

What they found:

• Some gray hairs regained color. This happened in both sexes, in several ethnic groups, at different ages and on different parts of the body.
• Graying, and the return of color, could occur at the same time as stressful events. In one case, five hairs on one person's head turned dark again during a vacation.
• Gray hairs had more of the proteins linked to energy use, mitochondria (the parts of a cell that produce energy) and antioxidant defenses. Columbia reported changes in 300 proteins when hair color changed.

The threshold idea

The team also built a computer model. It suggests that graying works like a threshold, and that crossing it can be undone for a while in some hairs. Picard explained the idea in the Columbia announcement. In middle age, hair may already be near the threshold because of biological age and other factors, and stress can push it over.

"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," he said. He added: "Reducing stress in your life is a good goal, but it won't necessarily turn your hair to a normal color."

A 2024 review in the Journal of Investigative Dermatology adds a related point: graying becomes permanent only when the stem cells in the bulge of the follicle are depleted. In the 2020 mice, those stem cells were lost, and the gray did not go away.

What is still unknown

Several important questions remain open:

• Scale. The human study included 14 people. It shows that color changes and stress can happen at the same time. It does not show how much stress adds to graying across the population.
• Mice and people. The 2024 review cautions against applying findings from mouse models directly to humans.
• Stress compared with other factors. A 2020 study of nearly 1,000 people in Poland found that age explained far more of the differences in graying than genes did. How stress fits alongside age and genes is covered in genetics and gray hair.

One more point is worth making clear. Stress acts on new hair as it forms at the root. A 2013 review of 196 reported cases notes that the formed hair shaft has no living cells, so it is not thought to be able to change on its own. Stories of hair turning white overnight have a different explanation, covered in our page on gray hair myths.

What this means in practice

The AAD lists trying to manage stress among the habits that may delay graying, but it also says these are temporary measures that will not fully prevent it. Managing stress is not a proven way to bring back color. The AAD says there are currently no effective medical treatments that add color back to hair. Our post on whether gray hair can turn back to color covers the rare exceptions, and gray hair in your 20s looks at early graying.

If gray or white hair appears suddenly, in patches, or with other new symptoms, see a doctor. This page is general information and not medical advice. For a full explanation of why hair loses its color, read our guide on why hair turns gray.

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