Ecological studies of marijuana

Recently there has a been a lot of hype about the potential for marijuana legalization to control the opioid epidemic. Press examples are here and here.

A number of ecological studies have been published on the topic, and findings from these investigations are more and more being commented on by the media or used in advertising:

Image available via http://www.wltx.com/article/news/local/verify/verify-do-states-that-legalize-marijuana-have-25-fewer-opioid-deaths/482535530

In my post on the University of Washington CHOICE Blog, I describe some of the problems with ecological study designs.