Where did you get your grays? You probably think of a rebellious child, a job that kept you up at night or a parent in failing health. In other words, you think of stress.

Turns out, you’re not far off. This study showed that genotoxic stressors, meaning any substances (internal or external) that can damage DNA, speed up the aging process by turning hair prematurely gray.

Let’s break it down: Your hair contains melanocyte stem cells in the hair follicle. Normally, as a new hair grows, some of those stem cells mature into melanocytes (melanin-producing cells that give your hair color). The remaining stem cells renew constantly so that your hair can keep producing color.

Under stress, that process goes haywire.

Researchers exposed mice to x-rays and chemotherapy (both genotoxic stressors), and found that the damaged melanocyte stem cells matured too early, leaving a smaller store of stem cells. As a result, the mice couldn’t produce enough melanocytes, or pigment-producing cells, and new strands were starved for color—hello, grays.

What does this mean for you? The stressed mice’s hair follicles actually mirrored elderly mice, suggesting that genotoxic stressors found in our environment (like the sun’s rays, household chemicals, and pollution) may drive natural graying.

If you want to keep that natural color, de-stress your tresses.