Many marijuana researchers have come out and publicly criticized Gladwell's article. The biggest sticking points were Gladwell's association of marijuana with violent crime and schizophrenia, both things he took from a book by Alex Berenson, which we've discussed multiple times how problematic his conclusions are.
When it comes to violence, Beatriz Carlini, a senior research scientist at the University of Washington’s Alcohol & Drug Abuse Institute, notes Gladwell says there was an increase in violent crime after marijuana legalization began in Washington. But what he fails to note, according to Carlini, is there was a decrease in violence the two years prior, and therefore crime levels have simply reached the point they were at in the years before legalization. And Benjamin Hansen, an economics professor at the University of Oregon, who showed that crime rates in Washington and Colorado have actually decreased since legalization.
Another thing Gladwell focuses on is a report by the National Academy of Medicine that showed a link between schizophrenia and marijuana use. But Ziva Cooper, a research director at UCLA’s Cannabis Research Initiative and one of the authors of the report cited by Gladwell, came out and publicly affirmed that the report does not mean that marijuana use causes schizophrenia.
All of this is to say that while Gladwell may be right that we need to examine the possible harms of marijuana legalization, the main points he focuses on are either misconstrued or demonstrably false.
(h/t Seattle Times)