Let me conclude by adding the following. You mentioned the data from Colorado. It is interesting that the increase was observed prior to legalization in 2014. Those figures are actually from 2009. The issue of non-medical cannabis arose in 2014. The whole commercialization of cannabis predates that, back to 2009, and increases can be seen.
Moreover, other reports indicate that it is not the change in legal status that leads to increased use, but rather the way it is regulated, whether that is decriminalization as is the case in Europe, or actual legalization of the consumption of non-medical cannabis. We must remember this and not demonize cannabis. This is important for the sake of consistency with the approach to alcohol and tobacco in particular.
The fact remains that cannabis is not an apple; it is not an ordinary commodity. That is why regulation is needed.