Robert DuPont is a drug war ideologue.  Happily, the NYT published rebuttals by Eithan Nadelmann and others.  

In reality, cannabis is an economic substitute for alcohol, opiates and other psychoactive substances, such that when cannabis use goes up, drinking and other drug use goes down.

Report spurs call to study marijuana’s potential in opioid-crisis fight 
http://www.theglobeandmail.com/news/british-columbia/pot-good-for-chronic-pain-but-more-research-needed-into-helping-with-opioid-crisis-report/article33613964/