People that are already going to have mental conditions when they are older will get them. So you could connect eating a grilled cheese to getting the mental conditions too, or playing poker, masturbating, kicking a rock, having sex with jesus, watching tv, driving a car, using a computer, drinking water, learning to read, playing video games, eating fish food, taking a shower in asbestos, or breathing at any point in the day. It's not a theory that can be tested very well. You can't have a subject that all they do is smoke pot until (and a bit past) puberty, to rule out all other variables. They'd die of starvation.