Stress Turns Your Hair Grey
"The old belief that a period of intense stress can cause your hair to turn grey, sometimes seemingly overnight."
Confirmed by Harvard researchers in a 2020 study published in Nature. Stress activates the body's fight-or-flight nervous system, which releases a chemical called norepinephrine near hair follicles. This causes the follicle's pigment-producing stem cells to burn through their reserves far faster than normal, and once those stem cells are depleted, the hair they produce grows in without colour, permanently. The mechanism was demonstrated directly in mice, and researchers separately documented a real human case: a 30-year-old woman developed grey patches in her hair that lined up exactly with the most stressful period of her year, a marital separation, and the colour partially returned once the stress passed.