Stress is the culprit behind grey hair

The real cause
Researchers found that the genotoxic stress damaged the DNA and reduced the melanocyte stem cells within hair follicles. As a result, these stem cells, responsible for making melanin, the pigment that gives color to hair and skin, lose their potency.

When the human mind confronts a tough situation, these stem cells do not fall off; instead they differentiate and form fully mature melanocytes themselves, giving the semblance of those silver strands.

Lead author of the study, Emi Nishimura, of Tokyo Medical and Dental University, said, "The DNA in cells is under constant attack by exogenously-and endogenously-arising DNA-damaging agents such as mutagenic chemicals, ultraviolet light and ionizing radiation.”

According to estimates, a single cell in mammals encounters close to 100,000 events that are detrimental to the DNA.

Nishimura said of the tendency of these cells, "Once stem cells are damaged irreversibly, the damaged stem cells need to be eliminated to maintain the quality of the stem cell pools. We have found that excessive genotoxic stress triggers differentiation of melanocyte stem cells."

The study
For the purpose of the study, Nishimura and her colleagues exposed mice to radiation and drugs used in chemotherapy. They then observed the alterations in the color of their hair as well as the condition of their stem cells.

The fur of mice turned gray prematurely and the stem cells in their hair follicles also matured very early. By scrutinizing the hair follicles under microscopes, the researchers established that stem cells had turned into other cell types and linked the change to the graying hair.

The study was published in the June 12 issue of the journal Cell.