The report does not discuss violent behavior specifically, which requires another leap. Berenson argues that if marijuana can cause psychotic breaks from reality, and psychotic people are more inclined to violence, marijuana is a cause of violence.

This is where he and Gladwell lose and upset some experts. Berenson specifically takes issue with the National Alliance on Mental Illness’s famous assertion that people with mental illness are more likely to be the victims than the perpetrators of violence. “Those statements are deeply misleading,” he writes, claiming that the subset of mentally ill people with schizophrenia is much more likely than average to be violent.

Yasmin Hurd, the director of the Addiction Institute at Mount Sinai School of Medicine, works on figuring out who is prone to addiction and why. She is among the small number of U.S. scientists who have authorization to study marijuana. “There is nothing to support that marijuana legalization has increased murder rates,” she told me. “The association between schizophrenia and marijuana use is nothing new. Early use of THC [tetrahydrocannabinol, the main active ingredient of cannabis], especially in high concentrations, is associated with psychosis and schizophrenia. That has been studied a lot. But schizophrenic people are not the ones committing murders. Trying to put a mental-health disorder as the explanation for murder rates—that is incorrect and should not have a platform.”

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Hurd also emphasizes, contrary to Berenson, that marijuana remains a promising alternative to minimize opioid use and dependence. “I’ve studied cannabidiol and found that it does have beneficial effects in reducing opioid use,” she says.

The consensus is that, yes, for most people there is such a thing as too much marijuana. In some cases, using too much can have severe consequences that many people could benefit from taking more seriously. There are documented instances in which people have been driven to violence by marijuana, though what Berenson describes mostly seem to be cases where marijuana use is heavy over the course of many years—which could itself be a result rather than a cause of a psychosocial problem.

In these and the other cases in which an occasional user ended up in a psychotic episode or violent fit, it seems mostly that the marijuana does the final unleashing. As with any drug that lowers inhibitions, marijuana is much less likely to bring forth an entirely new person than it is to expose the nature of a person formed over a lifetime of input and environmental exposures and genetic proclivities. Violence is always a multifactorial end point.

Gladwell makes the same basic point: “The experience of most users is relatively benign and predictable; the experience of a few, at the margins, is not. Products or behaviors that have that kind of muddled risk profile are confusing, because it is very difficult for those in the benign middle to appreciate the experiences of those at the statistical tails.” Those outliers, if you will, are where the headlines are made. They are the focus of both writers’ arguments. But they’re also the heart of the problem these arguments face in the first place: The question of exactly how muddled that risk profile actually is makes it impossible to say whether marijuana is “more dangerous than we believe.”