We basically have two choices. One, we can become a prohibitionist police state, accepting a high level of organized crime. Two, we can allow people to self-intoxicate freely with the understanding that no matter what they do they are still responsible for their own behavior. The evils of the former option exceed those of the latter by several orders of magnitude.
The other thing I'll note here is that anti-drug arguments are pretty much identical to anti-gun arguments (people can hurt/kill themselves therefore the government must stop people from having them). If you agree with the reasoning for the former, there's not much ground to stand on opposing the latter.
I am only commenting on the risks of using psychotropic drugs on undeveloped minds......I'm not giving any credence to prohibition or self intoxication etc......I'm only commenting on the fact that the neuropathways of the brain are easily influenced and may take years to change and in the case of adolescents, the optimum pathways could be damaged....unlike many here, i'm not digressing to other agendas or theorys.....