My anecdote can beat up yours :D
- can we identify groups who regularly use and don’t use - and isolate other lifestyle factors - and follow them for years of the life - and get them to accurately report data - and determine which life outcomes can be attributed to cannabis use
No study like that is going to be compelling. The anecdote is going to be just as useful in your personal life. It’s how humans learn.
Is it QED? No, the best that can be hoped for is, "Hmm, that's interesting".