The Grapevine

Scientists Uncover Reason Why Stress Causes Gray Hair

A new study has found the reason why people lose their hair color during stressful times. Researchers at Harvard University said hair graying occurs because of the permanent damage caused by stress to pigment-regenerating stem cells in hair follicles.

The study, published in the journal Nature, aims to help the medical community understand the direct impacts of stress on human health. People get gray hair when stress activates certain nerves that play a role in the fight-or-flight response, Science Daily reported.

Researchers analyzed how stress affects individual organ systems, from cell-to-cell interaction and to molecular dynamics. They used various methods that involved manipulating organs, nerves and cell receptors.

The team first thought that stress causes changes in the body because of an immune attack on pigment-producing cells. But tests with mice in the lab showed that hair graying occurred even in animals that lacked immune cells and the hormone cortisol.  

"Stress always elevates levels of the hormone cortisol in the body, so we thought that cortisol might play a role," Ya-Chieh Hsu, senior study author from the Alvin and Esta Star Associate Professor of Stem Cell and Regenerative Biology at Harvard, said. "But surprisingly, when we removed the adrenal gland from the mice so that they couldn't produce cortisol-like hormones, their hair still turned gray under stress."

Researchers then looked into the sympathetic nerve system, which is connected to each hair follicle on the skin. It also plays an important role in the fight-or-flight response. 

When the subjects experienced stress, the sympathetic nerves produced the chemical norepinephrine, which travel to pigment-regenerating stem cells. The chemical directly affected  the stem cells that color the hair and caused changes in the hair follicle.

“After just a few days, all of the pigment-regenerating stem cells were lost,” Hsu added. “Once they're gone, you can't regenerate pigment anymore. The damage is permanent."

The study would help guide scientists in efforts to understand the broader effects of stress on individual organs and even tissues, the researchers said. They hope that the findings would also help in the development of treatments or methods to modify or block the damaging effects of stress.

woman gray hair A study found a link between stress and hair graying. Pixabay