“there are uncountable people who have smoked high-grade marijuana regularly for decades. ”
ZK, Mark Kleiman of UCLA has been writing about the topic of very heavy marijuana users for a while, and I find his work convincing. He is far from a drug warrior, and was hired by Wash state to implement its legalization. He is pretty concerned about the effects of legalization on this group, and also the easier access to young people to high THC product.
There really is evidence that heavy use is pretty bad for you. What it comes down to is whether the heavy users would have been heavy drinkers otherwise, in which case the substitution is a net positive.
