@ArmamentHero:
That depends. There's been plenty of cases where they had it pre-existing, but just manifested out of nowhere.
One can be born with a disorder (because of birth complications, parent genes, etc), and one can develop it as a response to stress, actual reason for that is very complex and not completely understood.
But, one can be treated to, for example, consider consequences of one's actions (even if one cannot comprehend them completely), or to control violent tendencies etc. It depends on threatment and people around, so same individual with a disorder can become completely asocial psychopath or functioning member of society.
–- Update From New Post Merge ---
@King:
Uh, Rosi lived in the same environment as Doula and went through the same suffering, but was still able to remain a nice person.
Don't act like there haven't been cases of good parents in good environments having mean children.
It's almost like you didn't read last sentence. Yes, they reacted differently, and you are actually proving my point because there can be mean children in good families because of parents pedagogical incompetence (no matter how good they are), and there are good children in bad families who develop urge to be nothing like their parents and be good. Roci became a nice person for some reason, Doffy became a pirate. That doesn't mean either of them was born with angel/devil wings.