What would cause a preteen to have gray hair?

I was playing with my daughter's hair(she's 11) and found a gray hair in her bangs. What would cause this?What would cause a preteen to have gray hair?
Maybe she is stressed out about something from school. You should ask her if she is worried about something. What would cause a preteen to have gray hair?
I had a best friend that was totally grey by the age of 13. It was just her genetic make-up and nothing she could've done would've changed it. I hope that isn't the case for your kid because it may mean a lifetime worth of dye! haha Really I know a few people that have had this and it stunk, but it was normal.
I'm not sure the reasoning behind it, but it happens to people. One of my friends has always gotten gray highlights in her hair in the summer time. Some people just gray early. It could be a lack of pigment in the hair strands? I'm not a hair professional.
if premature gray runs in the family.