Substance Abuse and Native Americans
This is an OPINION and I'm not going to explain, justify or try to support it.
I suspect that you see a lot of substance abuse in Native Americans at least in part due to infections introduced by European colonizers that Natives had no immunity for.
We do know an awful lot of tribes were wiped out or decimated by European diseases.
If you think that's not just bat shit insane and you find my idea interesting, you may wish to read the following pieces by me as well: