Why did my hair turn grey so early?

I started slightly turning gray when I was 12 or so. Now I have tons of gray hair I've heard that it can and cannot come from stress. My father has epilepsy and I've heard things recently saying children of epileptic parents have many disorders. I have bad stress management ADD and OCD not clinically diagnosed but I have all the symptoms and people tell me I have these all the time. Are these all related in anyway? Thanks.