It is been said that stress turns hair white. Zang and collaborators published on Nature the research, which gives us the confirmation of this popular saying.
Long story short: stress triggers the fight-or-flight response, which has an impact on the cells producing hair pigments.
Going into details of the experiment, researchers stressed mice by injecting them some stimulating molecules and waited. After five days, mice turned white. At the beginning, the scientists thought that the immune system or cortisol could be responsible for the color changing. But after eliminating these two possible causes, they found the real culprit: the nervous system.
Follicles contain some special stem cells which are responsible for the hair color. In a stressful situation, the fight-or-flight response is activated, the nervous system releases noradrenaline and the body needs uses most of his stem cells, including the one responsible for hair color. Since these cells are used, hair turns white.
The next questions the researchers want to ask is whether the grayness of hair correlated with age follows the same mechanism they just discovered.
Zang et al., “Hyperactivation of sympathetic nerves drives depletion of melanocyte stem cells”, (2020), https://doi.org/10.1038/s41586-020-1935-3