Sure. I have two quick comments.
First, I studied the cannabis substitution effect. The first study on this that I'm aware of was by a researcher named Karen Model, who looked at U.S. states that had decriminalized cannabis in the 1970s. She found a reduction in ER visits and in alcohol-related driving incidents in U.S. states that had decriminalized cannabis. That seems to contradict a little bit of what we've heard.
Just to quickly finish off, I think no matter how you feel about the impact of cannabis on the young brain, I'm just not sure whether arrest and prosecution are the best ways to reduce that impact.