Scientists have found evidence that points to long-standing anecdotes that stress causes gray hair. The researchers found that types of nerves in mice involved in the fight-or-flight response were the pigmented onesStem cells in the hair folliclepermanent damage. The results expand knowledge about how stress affects the body. This is also a first step in blocking the negative effects of stressful conditions.
How does gray hair occur?
Anecdotes have long linked stressful experiences with the phenomenon ofgraying of hair. Now, for the first time, scientists at Harvard University have discovered exactly how this process occurs. Since stress affects the entire body, the researchers first had to narrow down which body system was responsible for the connection between stress and hair color. The team initially hypothesized that stress triggers an immune attack on pigment-producing cells. When mice lacking immune cells still showed gray hair, the researchers turned to the hormone cortisol. But that again turned out to be a dead end.
“Stress always increases levels of the hormone cortisol in the body, so we thought it might play a role,” said lead author Ya-Chieh Hsu, the Alvin and Esta Star Professor of Cell and Regenerative Biology at Harvard. “Surprisingly, when the mice were unable to produce cortisol-like hormones, their hair still turned gray under stress.”
After the team systematically eliminated various possibilities, the researchers focused on the sympathetic nervous system. This is responsible for the body's fight or flight response. Sympathetic nerves branch into every hair follicle on the skin. So scientists found that stress causes nerves to release the chemical norepinephrine. This is absorbed by the nearby pigmenting stem cells. The finding underscores the negative side effects of an otherwise protective evolutionary response, the researchers said.
“Acute stress, particularly the fight-or-flight response, has traditionally been viewed as beneficial to an animal's survival. “In this case, however, acute stress leads to permanent stem cell exhaustion,” said postdoctoral researcher Bing Zhang, the study’s lead author.
Finding the reason for gray hair
To link stress to graying hair, researchers first started with a whole-body response. They gradually investigated individual organ systems, the interaction from cell to cell and finally down to molecular dynamics. The process required a variety of research tools, including methods for manipulating organs, nerves and cell receptors.
The results may help shed light on the broader effects of stress on various organs and tissues. This understanding will pave the way for new studies that attempt to modify or block the harmful effects of such overload.
“By understanding exactly how stress affects stem cells and pigment regeneration, we have laid the foundation for understanding how stress affects other tissues and organs in the body. Understanding how our tissues change under stress is the first critical step toward potential treatment that can stop or reverse the harmful effects of stress. We have to goour studystill learn a lot.”
