While I don’t personally believe our knowledge of brain development is high enough to truly understand the effects I do however respect that we might need an age limit on alcohol and tobacco and marijuana. That said, I don’t think we fully understand enough about the brain or marijuana effect on it to really answer your question.

There are cases where I would support oils and other medicinal uses of marijuana in children though but again our research on marijuana I think has been severely broken by refer madness and the political and legal restrictions on cannabis research.

I would argue though that if you can sign up for the military and possibly die for your country that you should be able to smoke a joint, drink beer and have a cigarette. Which in my country usa is 18 I think

TLDR: I don’t know