I totally agree that the war on drugs has been an abysmal failure … unless, or course, the actual purpose was to disrupt communities of color, build the largest per capita prison population in the world (724 per 100,000 in the U.S., compared to 581 per 100,000 in Russia) and stigmatize people with drug dependency so that they won’t seek help until it is too late.

That said, I did not intend to imply that mental illness is the fault of a single drug. But there is good evidence that people in late adolescence and early adulthood, who are at high risk for developing schizophrenia (e.g., have other family members with the disease) should avoid not only cannabis but most other recreational drugs. I agree that cannabis use can have value both as a medical and a recreational substance for many people, but the risk is simply not justified for some.