Many of the early studies weren’t high quality studies. And as I recall a couple were outright fabricated. It takes time to run randomized prospective studies and those are coming out now.
What is the high quality study here to prove?
I don't see why the problem is evidence. AFAIK there seems to just be a shortage of people repeating "the helpful effect is geographically correlated" over and over again. Unless there is evidence of a positive effect that I'm not aware of?