Many people believe that stress can cause grey hair, but until recently, scientists were not sure how this happens. A new study from Harvard University has finally found the reason. The researchers, led by Ya-Chieh Hsu, showed that stress can damage special cells in the hair that help keep its color. Their work was published in the scientific journal Nature.
The team wanted to answer a simple question: does stress really cause hair to turn grey, and if it does, how? Since stress affects the whole body, they started by looking at different systems to find the one responsible.
At first, they thought the immune system might be attacking the cells that give hair its color. But even mice without immune cells developed grey hair when under stress. So the scientists looked elsewhere.
Eventually, they focused on something called the sympathetic nervous system. This is the part of the body that helps us react to danger or stress. It’s what causes the “fight or flight” response when we feel scared or under pressure. These nerves are found all over the body, including in the skin and hair follicles.
When we feel stressed, these nerves release a chemical called norepinephrine. Normally, this helps the body get ready to act.
But in the hair, it does something different. It reaches the cells that make hair pigment—these are special stem cells that stay in the hair follicle and wait until they are needed. When the hair grows back, these stem cells become pigment cells and give the hair its color.
But when stress causes a rush of norepinephrine, it makes these stem cells become pigment cells all at once. This uses up the entire supply too quickly. Once they are gone, there are no more stem cells left to create new pigment cells. That’s why new hair growing in will no longer have color—it turns grey or white.
This is the first time scientists have clearly shown how stress affects hair color in this way. It’s a surprising result, because the fight-or-flight system is meant to protect us, not cause harm. But in this case, it has a side effect that was not expected.
To understand the process fully, the researchers didn’t just look at hair under a microscope. They studied how the body reacts to stress at different levels—from whole organs down to individual cells. They used many tools to test how organs, nerves, and molecules interact.
While turning grey is not dangerous, this study helps us understand how stress affects the body more deeply. If stress can cause this kind of damage in hair, it might also harm other parts of the body in similar ways. The more we understand these changes, the better chance we have to prevent or treat them in the future.
This discovery might lead to new treatments to stop or slow down some of the effects of stress. Although grey hair is harmless, it could be a sign that stress is affecting the body in more serious ways.
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