Anecdotal evidence of stress leading to grey hair has been known for a long time. However, until now, the mechanism behind this association has been left up to speculation. A recent study has been published in Nature magazine from researchers at the Harvard University Department of Stem Cell and Regenerative Biology; it seems to reveal the cause of this interesting association.
At first, these researchers thought that the cause of greying might be the stress hormone cortisol, produced in the adrenal gland. However, lab mice who had their adrenal glands removed still showed a transition of greying hair under stress. So, the researchers went back to the drawing board.
The key to this mechanism turned out to be the sympathetic nervous system, or SNS. Colloquially known as the “fight or flight” response, the SNS prepares the body for intense bouts of physical activity or high-pressure situations. The inverse of this system is the parasympathetic system, or PNS, which relaxes the body (what some like to call the “rest and digest” response). When the SNS activates, it signals the adrenal gland to produce not only cortisol, but also other stress hormones like epinephrine and norepinephrine. These hormones cause a variety of effects, including elevated heart rate and blood pressure to prepare you for activity.
SNS nerves branch throughout the body, including into each hair follicle, which is the sheath of cells and connective tissue that surrounds the root of the hair. These follicles contain adult stem cells (a complex type of cell that can develop into several different types of cells). As hair grows and regenerates, some of these stem cells develop into pigment-producing cells and create our hair’s pigment compounds. In the current study, it was found that the stress hormone norepinephrine causes stem cells to activate excessively. This causes them to all convert into pigment-producing cells, prematurely depleting the reservoir. With no regular stem cells to divide, reproduce, and continue differentiating, the pigment eventually runs out. This causes the hair to grey sooner than it would naturally by old age. This damage is also permanent within the individual hair strands.
This study shows potentially severe health implications to high stress lifestyles. With the hair and skin being the most prominent bodily tissues we can see from the outside, the effects of stress are often apparent. However, the stress response is also likely affecting other tissues in the body that are not immediately visible. Ya-Chieh Hsu, the senior author of the research paper, had this to say:
“By understanding precisely how stress affects stem cells that regenerate pigment, we’ve laid the groundwork for understanding how stress affects other tissues and organs in the body. Understanding how our tissues change under stress is the first critical step towards eventual treatment that can halt or revert the detrimental impact of stress. We still have a lot to learn in this area.
Ya-Chieh Hsu, Associate Professor of Stem Cell and Regenerative Biology at Harvard
Original story and interview by Jessica Lau of Harvard University.
References
- Zhang B, Ma S, Rachmin I, He M, Baral P, Choi S, Gonçalves WA, Shwartz Y, Fast EM, Su Y, Zon LI, Regev A, Buenrostro JD, Cunha TM, Chiu IM, Fisher DE, Hsu Y-C. 2020. Hyperactivation of sympathetic nerves drives depletion of melanocyte stem cells. Nature.
- 2011. Understanding the stress response. Harvard Health. Harvard Health Publishing.
- URMC Health Encyclopedia. URMC Health Encyclopedia. University of Rochester Medical Center.
American Biologist 