When he was 10, she left the family to pursue her career as an art history professor. That sort of utter rejection from the maternal figure in your life, at that prepubescent age... Wow. And it's totally unnatural on her part. I don't know, something is screwed up with her to be that selfish.
Anyway, shortly after that when his parents became officially divorced is when he first became "addicted." He also tried to commit suicide when he was 14. This video game crap is just a method of escape. It's creepy how he will talk like the characters and get SO into the game like that.