- Researchers establish a link between stress and hair graying.
- Under stress, sympathetic nerves release the chemical norepinephrine, which plays a major role in stress-induced hair graying.
Stress can have several adverse effects on the body. One popular belief about acute stress is that it can cause hair to turn gray. However, it hasn’t been scientifically proven. Whether stress-related changes occur at the level of somatic stem cells and whether external stressors are the causal factors, remain poorly understood.
Now, for the first time, researchers at Harvard University have found how exactly stress changes the color of hair. In other words, they have scientifically linked the stress with accelerated hair graying (formation of unpigmented hairs).
Actually, the color of hair is determined by melanin-producing cells known as melanocytes. They are produced by melanocyte stem cells that reside within the hair follicle at the base of the hair strand.
Since melanocyte stem cells begin to disappear as we age, the hair that regrows from hair follicles contains less pigment and appears grayish.
To find out how stress can cause gray hair, the research team conducted experiments with mice. They exposed mice to 3 kinds of stresses: psychological, short-term pain, and mild stress. This resulted in a noticeable loss of melanocyte stem cells and hair graying.
After establishing a connection between stress and hair graying, the team explored various potential causes. They tested whether melanocyte stem cells might be reducing due to the immune attack. However, the stressed mice with compromised immune systems also grew gray hair.
They then explored hormone cortisol in the body; by changing its level, they found that it is not responsible for stress-related graying.
Key To Stress-Induced Hair Graying
After eliminating various possibilities, the team focused on the sympathetic nervous system that controls the body’s fight-or-flight response. These nerves branch out into each hair follicle.
Under stress, sympathetic nerves release the chemical norepinephrine (also called noradrenaline), which causes the stem cells in the hair to activate excessively. These stem cells eventually turn into pigment-producing cells.
This prematurely depletes the stem cells, and when new hair is made, there are no stem cells left to make pigment cells. Because of the lack of pigment cells in the follicle, the hair turns gray.
Stress depletes stem cells, causing hair to turn gray in mice | Courtesy of researchers
Once these stem cells are gone, they cannot be reproduced: the damage is permanent.
To establish a link between stress and hair graying: researchers went from the highest to the smallest level of detail. They began from the whole-body response and progressively moved to individual organ systems, cellular interactions, and molecular dynamics.
To explore these systems, they utilized various technologies along the way, including the techniques of manipulating nerves and cell receptors.
Neurons are known to regulate blood vessels, organ functions, and immunity, but how do they regulate stem cells isn’t well-understood. The findings explain how neurons control stem cells at molecular and cellular levels, linking stress with hair graying.
The study can also help scientists reveal the wider effects of stress on different organs and tissues. This will open new avenues for studies that seek to alter or block the negative effects of stress.