My answer to Does stress cause white/gray hair?
Answer by Nature Crazy:
Yes, while stress can cause accelerated hair loss it is also involved in premature graying too. Melanocytes, the source of the color of hair, go through a rapid cell destruction process in the aging hair follicle. Eventually melanocytes completely die off, leaving no color left. You’ve probably noticed that many President’s go through a quick acceleration of graying hair due to the stress factor.