And furthermore wrt Daniel and whether or not he was on any drugs other than Lexapro, there was testimony by Birkhead that he was told to lock her bedroom door when she was so high because she didn't want Daniel to see her that way.
Reading between the lines there tells me that Daniel didn't approve of her drug use and may not have been a user himself. Think about this, if he was on methadone and his mother was Anna Nicole Smith, he'd be an addict. He could afford as much of it as he wanted. You don't just do methadone one time and say "eh, i didn't like it". That methadone was likely Anna's not his.
I believe it was her's. A hair test would tell the story.