How Dangerous is Marijuana, Really?
On Jan. 7, The Marshall Project published an interview with Alex Berenson, a former New York Times reporter and author of "Tell Your Children: The Truth About Marijuana, Mental Illness, and Violence," which warns that the rush to legalize the drug has obscured evidence of its dangers. The interview stirred up a storm on social media, so we decided to enlarge the discussion.
What follows is a conversation, conducted by email and moderated by Bill Keller, editor-in-chief of The Marshall Project. Berenson is joined by three other panelists. Maria McFarland Sánchez-Moreno is the executive director of the Drug Policy Alliance, a non-profit that advocates ending the war on drugs, including the "responsible regulation" of marijuana. Its donors include companies in the legal, for-profit cannabis industry, whose gifts, the group reports, made up less than 1 percent of the alliance’s 2018 revenue. Keith Humphreys is the Esther Ting Memorial Professor at Stanford University. He has been deeply involved in drug policy as a researcher and White House advisor. Mark A.R. Kleiman is a professor of public policy at the New York University Marron Institute of Urban Management, where he leads the crime and justice program. He is also chairman of BOTEC Analysis, which advises Washington State and Maine on cannabis regulation.
The discussion has been lightly edited for length and clarity.
The Marshall Project: This first question is for all of you. Let's start with the core question Alex set out to answer in reporting his book: What do we know about the connection between marijuana and mental illness? What would you say is established medical science, and what is still unresolved?
Alex Berenson: Okay, I'll jump in. Marijuana causes psychosis. This is an established medical fact, not open to debate. It can cause temporary psychotic episodes even in healthy people. It worsens the course of schizophrenia and provokes severe relapses in people with schizophrenia whose disorder was controlled.
The mainstream literature and the physician-scientists who have done the most work on the issue also believe it is responsible for some cases of schizophrenia that otherwise would not have occurred—that is to say, that it can cause schizophrenia, especially when used regularly to heavily by adolescents. The advocacy community focuses on that part of the issue and overstates the uncertainties surrounding it, which after 30 years of research are relatively minor, and probably relate more to risk ratios than anything else. But in doing so, advocates elide an equally significant issue. Even if marijuana did not produce a single de novo case of schizophrenia, its use frequently causes temporary episodes of psychosis. To say otherwise is to ignore the reality of emergency rooms all over the United States.
Keith Humphreys: I am going to start by making a distinction, which I will rely on throughout this discussion, between "old cannabis" and "new cannabis".
By "old cannabis" I refer to the drug that was dominant in the U.S. throughout the 20th century. It was a plant, almost always smoked, that had single-digit percent THC content and significant CBD as well. Its user base included many people who smoked only occasionally, once a week or once a month. [THC is the chemical in pot that gets you high. CBD is a different chemical that can buffer the effects of THC.]
By "new cannabis" I refer to the drug that has been become dominant in the past 5-10 years. It is very high in THC (average 20 percent in Washington's legal market), lower in CBD and is consumed in a range of ways beyond smoking. Its user base includes many people who consume it every day or nearly every day.
It's very unlikely that the effects of old cannabis and new cannabis on population health are the same. This is critically important because almost all our research is on old cannabis; by definition any study asking "what does cannabis consumption do over 10 years" is a study of old cannabis. I therefore feel much more humble speculating about the impact of new cannabis than old cannabis.
So, for Bill's questions.
