But the study would be okay if they merely interviewed individuals who purchased cannabis for their own recreation? What if these individuals were using it recreationally according to a schedule suggested by the interviewers?
Suggesting that study participants use a drug of unknown purity, composition, and dosing would definitely not be ok or safe. Encouraging illegal activity generally is not ok. Interviewing self-professed users without instructing them to use the drug would likely be ok but of limited value.
I don't know about other legal states but here in Washington the purity, composition, and dose of cannabis products are highly regulated and come with standardized labels.
Now sure, but what about 40 years ago?
We're discussing now, not the sociopolitical environment of the 1970s. Please stay on topic.
Parent did not say they would be purchasing in a state where recreational dispensaries exist or where weed is legal at a state level. Those are unstated assumptions.
Maybe an independent group could manage the schedule and have lab tests done so the drug details could be determined. Then the academic researchers could track the subjects, analyze the results and publish.