Addiction is a song that talks about the dark side of toxic people. in this case it was a guy who cared deeply about a girl, but she always went for the guy who'd treat her like she doesn't matter, and before anyone had noticed something was going on it was already too late. The guy was supposed to move on from the girl but somehow he always gets sucked back into her world, he is addicted to her just as she is to the other guy.