"Province Alphaville" in the High French Speaking part of Canada, has a vote and decides to go "alcohol free" for the next 30 years. Province consents to cross-sectionally divide itself for controls into sub-cohorts, where: Cohort A - has legal access to psychedelics, B - to marijuana, C - to something else TBA, D - to no intoxicants not even tobacco. And we just observe over time. Surely some place in the world / large enough group of people would be willing to sort themselves like this. Then with a large and diverse enough population I think we can clearly get some good data and mostly lay the question to rest as to the "health effects" of chronic use of various intoxicants/inebrients/entheogens/empathogens/whatevers :) ;P xx ;p