Cannabis, alcohol, and public safety: Knowing what you don’t know

Cannabis might be a substitute for alcohol. Or they might be complements. Right now, we just don’t know.

[See update and correction below. Apologies to Adam Nagourney and Rick Lyman.]

The main problem with journalism, in a world full of unknowns and uncertainties, is that faith is news and doubt isn’t. 

Mark Anderson of Montana State and Daniel Rees University of Colorado at Denver presented an interesting paper at this year’s meeting of the International Society for the Study of Drug Policy, using some moderately sophisticated statistics to investigate the relationship between cannabis availability, alcohol consumption, and traffic accidents. The paper moved my opinion about whether cannabis and alcohol are substitutes or complements from “Not a clue; could go either way” to “There’s a little bit of evidence for substitution” (that is, for the proposition that making pot more available or cheaper would lead to less heavy drinking).

Net substitution would be a big deal, if true, because alcohol does so much more harm than cannabis that a small reduction in the alcohol problem would, in social-cost terms, outweigh even a big increase in the cannabis problem due to legalization.

I say “a little bit of evidence” because the change in cannabis availability due to medical-marijuana laws is poorly measured; because the changes in cannabis availability due to medical marijuana laws are small compared to the changes that would result from full legalization; and because the short-term effects might not only be larger or smaller than, but might not even be in the same direction as, the long-term effects. (Remember the guy who jumped off the Emprire State Building. Being asked as he passed the fiftieth floor, how the experiment was going, he replied, “So far, so good!”)

Unfortunately, Anderson and Rees decided to build on their finding, and other findings from the literature, to make a strong claim: “We expect that the legalization of recreational marijuana in Colorado and Washington will lead to increased marijuana consumption coupled with decreased alcohol consumption. As a consequence, these states will experience a reduction in the social harms resulting from alcohol use.”

Even more unfortunately, Adam Nagourney and Rick Lyman  of the New York Times decided to take that claim at face value, ignoring the papers in the same issue of the same journal by Rosalie Pacula of RAND and Eric Sevigny of the University of South Carolina arguing that the Anderson and Rees claim is more than the current data can support.

Pacula and Sevigny didn’t make the opposite claim: that legalization will increase heavy drinking. Had they done so, normal journalistic practice would have been to cite the two conflicting opinions. But since they brought in the Scotch verdict of “Not Proven,” Nagourney and Lyman simply ignored what they had to say. That let them use the Anderson and Rees claim to support the theme of the story, well-captured by the headline “Few Problems with Cannabis for California.”

[Update and correction:

The above paragraph is inaccurate about the sequence of events. Adam Nagourney writes:

You were wrong to assume I was aware of the dissenting studies and chose to ignore them. I was not; if I was, I most certainly would have mentioned the concerns. Professor Rees  gave me an advance copy of their study; I did not have an advance copy of the journal. Again, if I had, I most certainly would have raised the fact that other people question their assertions.
As someone who has been doing this a long time, I can tell you that this: “The main problem with journalism, in a world full of unknowns and uncertainties, is that faith is news and doubt isn’t” is not true, at least for me or the place I work. One of the great things about the New York Times is that there is room for nuance and subtly. A story is stronger journalistically if it addresses both sides of an argument.

This time I have to give myself an F in Journalism 101; I should have checked with Nagourney before criticizing his work.

Very sorry, sir! Won’t happen again, sir!]

In order to know how cannabis legalization would affect heavy drinking, you’d have to know:

1. The extent of the price decline.
2. The extent of the change in other conditions of availability and use (convenience, marketing, perceived product quality and variety, stigma, legal consequences, social customs).
3. The responsiveness (“elasticity”) of demand to price changes, consisting of two components: the “participation elasticity” measuring changes in how many people use cannabis at all, and the “conditional elasticity” measuring changes in consumption-per-user.
4. Ditto for responsiveness to changes in non-price factors.
5. The “cross-elasticity” between cannabis and alcohol.
6. For all of these, you’d need estimates about the long-term effects of lasting changes, not the immediate effects of transient changes.

All Anderson and Rees can show are reasonable but not perfect estimates of the short-term effects of relatively small and poorly measured short-term changes in price and availability on various outcomes. They’re not within a million miles of being able to offer the sort of prediction on which one ought to base public policy.

For example: One likely impact of legalization, as Anderson and Rees note, is increased cannabis use among minors. Even if it were known that cannabis and alcohol are, at a given point in time, substitutes for minors, that wouldn’t show that increased pot-smoking by sixteen-year-olds might not increase their risk of becoming heavy drinkers at twenty-one. And the Anderson and Rees methods don’t even look for such long-term effects.

“It’s not what you don’t know that hurts you,” said Will Rogers. “It’s what you know that ain’t so.” Knowing what you don’t know doesn’t get your name in the newspaper. But it saves you having to eat your words. Since I think that cannabis legalization of some sort (1) is probably a good idea and (2) very likely to happen in any case, I devoutly hope that Anderson and Rees turn out to be right. But it seems clear to me that Pacula and Sevigny have the stronger argument. We just don’t know.

Author: Mark Kleiman

Professor of Public Policy at the NYU Marron Institute for Urban Management and editor of the Journal of Drug Policy Analysis. Teaches about the methods of policy analysis about drug abuse control and crime control policy, working out the implications of two principles: that swift and certain sanctions don't have to be severe to be effective, and that well-designed threats usually don't have to be carried out. Books: Drugs and Drug Policy: What Everyone Needs to Know (with Jonathan Caulkins and Angela Hawken) When Brute Force Fails: How to Have Less Crime and Less Punishment (Princeton, 2009; named one of the "books of the year" by The Economist Against Excess: Drug Policy for Results (Basic, 1993) Marijuana: Costs of Abuse, Costs of Control (Greenwood, 1989) UCLA Homepage Curriculum Vitae Contact:

36 thoughts on “Cannabis, alcohol, and public safety: Knowing what you don’t know”

  1. Mark:

    Do you happen to know if there are any good data on what happened to the black market for marijuana during Prohibition? Not that this would be very robust but perhaps of historical interest.

    I figure that there are probably some decent data on the effects on alcohol consumption in countries which have repealed or relaxed marijuana laws. Do those data shed any light on these questions?

  2. 1. Nice idea, but recall that marijuana was only slowly becoming illegal during alcohol prohibition. In most of the country, cannabis was legal while alcohol was illegal.

    2. No country has legalized cannabis production for commercial sale. The Netherlands has sort-of-legalized retailing, but production is still punished, and prices aren’t much lower than illicit-market prices. The changes were slow enough to make it hard to measure any impact on drinking, but the Dutch manage to put away a fair amount of beer and gin.

      1. The Uruguayan Senate hasn’t even voted yet. Assuming the law passes, it will be months if not more before cannabis is legally available. As of now, there’s nothing to look at save the bhang market in parts of India.

  3. I can currently choose to play a variety of contact sports: gridiron, rugby, ice hockey, roller derby, water polo, lacrosse etc.

    Now imagine if only gridiron (hello head injury) were legal but there was a movement to legalise ‘even more’ contact sports (why would you do that!? We have enough problems with just one!)

    Would I be sitting here reading Mark Kleiman’s cautionary analysis of whether gridiron and [say] lacrosse may or may not be substitutes? And what bearing would this analysis have on whether lacrosse should be legal?

    1. Of course it would be relevant. If introducing lacrosse caused more people to play football, it would increase head injuries twice: directly, and by increasing football head injuries. Now, I can’t imagine offhand the mechanism that would bring about such a result, but if that were the fact then increased head injuries would be among the disadvantages of allowing lacrosse.

      And yes, on current envidence I would support a ban on football for people under the age of 21 unless they could demonstrate that they had no brains to injure.

      1. And yes, on current envidence I would support a ban on football for people under the age of 21 unless they could demonstrate that they had no brains to injure.

        Spoken like a gentleman who never met a ban he didn’t like. I’ll bet you’d support a ban on backyard swimming pools too, “on current evidence”. And bicycles. And skateboards. And trampolines. And just about any other fun but potentially harmful activity that a minor might want to engage in and a responsible parent might reasonably decide to allow (in the absence of laws overriding their parenting decisions advocated by others who assume they know better). Let me know when you’ve figured out how to protect children from everything that might cause them serious harm. Better start with transportation. Children should be kept safely at home wrapped in bubble-wrap until age 21, right?

        Overprotection isn’t good for children, or for society. Going overboard in attempts at harm reduction produces harms of it’s own, which commonly effect more people more adversely than the harms we attempt to reduce. Witness the drug war, for example. This vision of Utopia which goes so far as to ban children under 21 from playing football looks like a hellish nightmare scenario to me.

    2. We could try to design a triathlon-type contest of multiple contact sports that would give high-testosterone types the maximum opportunity to injure themselves and others everywhere but on their heads. Ice hockey, followed by water polo, followed by roller derby perhaps. I’m not sure lacrosse is sufficiently dangerous to make the cut crash.

        1. That existed once, more or less; it was bare-knuckle prizefighting. Rules. Blows to the head were not illegal, but I understand impracticable because the puncher would break his knuckles. Matches could last for hours (record 6 hrs 15 minutes), both pugilists covered in blood from injuries to the torso, and prizefighters could live in mental health to a ripe old age.

          Where did the conventions of Hollywood bar fighting come from, with its fictional bare-knuckle knockout blows to the chin?

          1. James you may be correct about the damage caused by gloves:

            Blows to the head cause two different kinds of injury. The face is cut and bruised by direct impacts, but damage to the brain is caused largely by rotational acceleration of the cerebral cortex around the much smaller midbrain and spinal cord. This damage may be aggravated by boxing gloves since they add weight and thus energy to punches, causing more rotational acceleration.


    3. I think your problem strayan is that you see the legality of cannabis as a moral issue, rather than one that can be solved by examining some costs of drug use. It’s like discussing the increase/decrease in the price of cotton and trying use that evidence to help determine whether slavery was good public policy or not. I have the same problem unfortunately.

      1. I think the technocrats are moralistic. Why do pot smokers have the burden of proof to show that no bad thing will happen if they legalize it?

        The only possible answer is that it is taken as a given that getting stoned is a moral failure.

  4. I think you have misplaced the burden of proof concerning footballers and brains… let me guess, too many early concussions?

    1. No, I just meant that a minor who could demonstrate he had no brain to injure – e.g., by wearing a Rand Paul t-shirt – might as well be allowed to play football.

  5. Fully funded grants/studies on substitution and other stuff. Oh, I dare to dream.
    Wa state is very interesting: State to Costco (oops) control of liquor, rec cannabis, medical cannabis, revenue, black market, etc.

    Next five years will be an interesting ride.

    Interesting comment from an LCB officer from Wa state: Safeway had about $72MM in sales in liquor, but almost $4MM from loss (theft).
    Now, Safeway have decided to create secure, access rooms rather than the open floor plans of booze. (Seattle area, I believe).

      1. But I like him. He only tells me facts that fit neatly with my prejudices.

        Seriously, though, he deserves far more respect than Kevin Sabet or David Frum on the issue.

  6. Pacula and Sevigny’s article is paywalled. Anderson and Rees’s article is open access. So they win the argument by default. Bad behavior – publishing behind paywalls – has consequences, if you are trying to to inform a public policy debate in a democracy.

    Weak evidence of substitution is stronger evidence of non-complementarity. So Mark’s fear of longer-term complementarity, while a priori reasonable, has no evidence from these studies to back it.

    1. In my field and likely in yours, there exist prestigious outlets that have mandatory paywalls, and others that permit the authors to spend money to lower the paywall on their article. It seems unnecessarily harsh to be so dismissive of paywalled articled when there remain such strong incentives to publish them (in terms of career success, not of anything corrupt).

      Also in my field, the author owns the copyright to the manuscript; the journal only owns the rights to the version they’ve spent money to typeset and otherwise modify to nicely fit the journal’s house style. You could always ask the authors for the manuscript …

      1. I was being deliberately harsh, but it’s time for frankness. The professional incentive may be to go along with the paywall because the journal is prestigious. But the system is wrong, mere parasitic rent-seeking, and should he condemned. Things change when leading academics with established reputations and prestigious tenured chairs like Cambridge mathematician Tim Gowers take a stand. I’m not, but maybe i can annoy a few into taking this seriously.

        There’s a specific issue in policy-related sciences that does not apply to Gowers’ number theory. If an academic is trying to communicate, as she should, to the general public as well as professional colleagues, it is not reasonable to expect them to pay for research articles. The taxpayer has already paid for the research one way or another. There is a wide category of non-academics like myself who may be tempted to take a look at a free article, but not pay for one. So for our group, the free article wins by default, as the paying one has removed itself from our consideration, with the subtext – albeit unintended and unconscious – “I don’t care what the rubes think.”

        PS: Leonhard Euler has uploaded 62 papers to arXiv, and he died in 1783!

          1. It’s an interesting and a scary story, but it’s completely unfair to distinguished, aspiring open-access journals like e-Life or the PLoS journals to confuse them with the bottom-feeding, profit-making essentially fraudulent journals that were the culprits caught out there. See for example Michael Eisen’s response to that report.

            More generally: open-access is a good thing, and should be encouraged. But that’s not something that can happen for free, and it’s not going to be easy. In the meantime, parallel manuscript-sharing services like the arXiv and PubMed Central need to be used more often.

          2. Eisen went over the top. Think of the alternative hypothesis — no paper is ever improved, no mistake is ever caught by peer review. If he is right about that, we should not even help our students by looking at their work. But he isn’t right, and he must know that from day to day experience in academia.

            I agree with you on the free lunchism of open access. All the open access model does is shift costs, it doesn’t eliminate them, and everyone agrees that someone else should pay. One could make the argument that the “government has already paid in some way”, but if that’s true for science really all products should be free because the government in some way supports production of virtually everything.

      2. FWIW from my very non-tenured self who nonetheless appreciates the public investment in my institution (shrinking as it may be every year), a pox on paywalls. Yes, I can log-in to them. No I don’t have a cozy office to leave a computer logged in on the campus network. But it’s not the inconvenience, it’s the principle of thing. Info may not be free yet (but it’s trying), but I believe that one of the duty’s of my profession is to make sure that knowledge is free.

        Besides, historians should be granted non-profit status on entering the profession, because that’s the reality for most of us. Nickels and dimes from a paywall might be useful, but aren’t as important as the gist of our work, which we find a few feeble ways of marketing, enough to keep us in warmth and, for those who can still drink, beer.

    2. The essays were published in the same issue of the same journal. I’ve replaced the link to the Pacula and Sevigny piece.

      In any case, this isn’t a question of who wins or loses. This is a question about how the world is. Anderson and Rees made what I think are excessive claims, and Pacula and Sevigny are appropriately cautious about believing them. Their mistake wasn’t about paywalls; it consisted in not sending out a press release.

      1. Maybe you’re in your office, and benefitting from an institutional subscription that applies to any access from an IP address on the university campus? Usually the journal will in that case have a little header someplace saying “access provided by University of Freedonia” or some such, but maybe not always, and you certainly wouldn’t have had to log in.

  7. I rather much think we wouldn’t be in this mess if the same standards Mark argues should apply to ending prohibition had instead been applied in deciding whether to engage in it in the first place.

    And that’s a problem for a lot of American public policy. It was enacted for political reasons by those who interests were considerably narrower than the good of all citizens. I believe we should be cautious about being overly cautious in trying new approaches to seemingly intractable public policy problems, because tolerance of the status quo in many of them is simply intolerable. Waiting for all the facts to come in otherwise may become a prescription for immobility. Arresting hundreds of thousands of Americans for marijuana, mass incarceration, bald racial inequity in the justice system, and the resulting marginalization of millions from participation in the workforce are hardly arguments for stasis in anticipation of the results of intellectually rigorous study.

    1. I rather much think we wouldn’t be in this mess if the same standards Mark argues should apply to ending prohibition had instead been applied in deciding whether to engage in it in the first place.

      Read before you post. Mark didn’t argue for cannabis prohibition. There are people who are interested in facts per se, and not just in pushing “the cause” irrespective of reality.

      1. I realize Mark didn’t argue for cannabis prohibition. My comments were made with respect to most of what has been done with regard to cannabis over the last 8 decades. If each and every increment of the ratcheting up law enforcement to enforce prohibition had been examined from an evidence-based, scientific approach to public policy, we’d never have been in this mess to begin with. At worst, we would have detoured toward sanity after the report from Nixon’s marijuana commission…

        That said, my point was that we should be equally cautious at this about tolerating the problems of prohibition as we are about demanding evidence-based solutions to the problems it created. Don’t let the perfect be the enemy of the good.

        Nothing there except the search for reality. Can anyone make a straight-faced argument that the arrest/convict/incarcerate model has any positive effect on marijuana use? I don’t believe so and neither do a majority of Americans. FAIL and there is now a limited window to change that before the corrosive effects of an unjust and unwanted law eats away the last shreds of credibility our justice system has with large segments of the population. At this point, there is limited patience and time to argue we need to wait to alter public policy until “all the evidence is in.” Political events will otherwise soon overtake the slowly grinding wheels of policy development. Just pointing out that the government no longer holds all the cards here and events like CO and WA’s legalization will soon make arguing about policy details irrelevant unless one is willing to move forward despite some uncertainties.

  8. Hat tip to Our Founder on the prompt correction and apology. That sort of intellectual honesty goes to the core of what raises RBC above most of the internet cacophony.

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