Is it normal to be 19 with graying hair

Some people go prematurely gray. As for stress, and hair turning white there's an interesting story online about a man who survived the sinking of the Titanic, and a few months later all of his hair turned white. I think I have significantly more white hair now two years after having left my ex-boyfriend than I did before I met him, but I was only with him about a year, a half.