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The Herb Column: Cannabis Dispensaries vs. Opioid Overdoses

UC Davis professor Greta Hsu on her groundbreaking study about cannabis availability and opioid-related mortality

Back Q&A Feb 25, 2021 By Eric Johnson

Greta Hsu is a professor of management at UC Davis.

Greta Hsu, a professor of management at UC Davis, has published a study showing that, nationwide, counties that allow access to legal cannabis dispensaries can expect a significant decrease in opioid overdose deaths.

The study, coauthored by Balazs Kovacs, an associate professor of organizational behavior at Yale University, and published in the British Medical Journal, is the first to gather statistics on two subjects — opioid-related mortality and the prevalence of cannabis dispensaries — from the 812 counties in the 23 states in the United States where cannabis was legalized and had dispensaries operating by the end of 2017. The study pointedly includes both medical and recreational dispensaries. Its findings show that as the number of dispensaries increase, the number of opioid deaths drop.

While it does not claim a causal connection, the study suggests that “providing alternative pain management could improve public health outcomes,” according to a UC Davis news release.

The decision to conduct a county-by-county study produced more useful data, Hsu says, pointing to the fact that dispensary laws vary. In Sacramento County, for example, only the City of Sacramento allows dispensaries, while in Yolo County, legal cannabis can be purchased in Davis, Woodland and West Sacramento. Amador County is one of many that have banned all cannabis-related business

Hsu holds a Ph.D. in organizational behavior and master’s degrees in statistics and sociology from Stanford University. She says she and Kovacs worked together at Stanford, and that, like her, he takes “a quantitative approach” to the discipline of understanding how social movements and businesses interact. Comstock’s spoke to Hsu about the study released in January.

What inspired you to look into this issue?

My coauthor and I first became interested in the increasing prevalence of legal cannabis dispensaries as an organizational issue. … We realized that our county-level database could also be used to examine whether the availability of legal cannabis in an increasing number of geographic areas has any implications for opioid misuse.

We don’t normally publish in public health journals, but given how serious the epidemic of opioid misuse and drug overdose deaths have become in the U.S., we thought it was an important issue worth investigation.

Your study found that an increase from one to two dispensaries in a county — just adding one storefront — is “associated with an estimated 17 percent reduction in all opioid-related mortality rates.” Were you surprised at that number?

We were not particularly surprised because there’s been earlier work that looked at legalization events at the state level and they have roughly similar percentages. … So we were actually reassured that what we found is roughly consistent with what other people have found. We’re just modeling it at a more fine-grained level.

That 2014 study in the Journal of the American Medical Association showed that opioid overdose deaths dropped in states that legalized medical cannabis. How does your study strengthen that evidence or add to the body of knowledge?

There are two themes. In the case of California, there was a temporal lag between the legalization event (in 2016) and when the state got the licensing and regulatory system up and running and you actually saw operations opening up. So we didn’t want to just study before-and-after the legalization event — we wanted to know (what transpires) before and after people actually gaining access to purchasing legal cannabis. …

And in a state like California, which has lots of counties, it doesn’t really matter for someone in Sacramento that a dispensary has started up in San Diego. So we wanted to model this at a level where the local population can actually access legal cannabis. We’re trying to model it more meaningfully. I think now we have more data that we can use.

Your study shows an even greater decrease in unexpected deaths from synthetic opioids — fentanyl and its analogs. Why is that a larger number?

The simplest answer would be that fentanyl is largely responsible for recent increases in opioid-related deaths. It’s the main culprit in recent years. … It may simply be because that’s where the deaths are occurring, but our research doesn’t allow us to get to that.

How clearly does your study suggest that people will use cannabis as a pain medication, if it’s legal and easily available, rather than opioid painkillers?

If we really wanted to get into the question of whether people substitute or move over, we can’t get at that. All we can say is increasing availability, making cannabis legal, seems to decrease opioid-related mortality rates. One plausible story is that it’s because people are moving to a less-harmful substance when they need to manage pain. But we don’t know for sure.

You included recreational cannabis dispensaries, and not just medical cannabis dispensaries, in your study. Why is that?

We’ve seen other studies that focused specifically on the legalization of medical marijuana. Recreational was an open question because it’s a newer form. We decided to include it because we have the data, but also because we wanted to know: Is there something different about making cannabis legal recreationally versus medically? And there doesn’t seem to be a marked difference. Both seem to result in a reduction.

You cite evidence that opioid-related mortality rates increased significantly in 2020. How does that relate to the COVID-19 pandemic?

This is where we’re getting into speculation. But it does seem from several studies that there was an increase in overdoses during 2020. It’s not my direct study but one can only speculate that the isolation and the strain and the stress that people are being put under could drive people toward (opioid painkillers). But this is outside my realm of expertise.

How would you like to see the results of this study put to use?

While obviously we’re not showing any sort of causation, and it’s important to be clear on that, we do think we need to better understand the public health outcomes of cannabis legalization and think about how it affects other types of drug misuse. I think it is an important theme as we’re weighing the potential benefits versus harms of promoting cannabis legalization.

So we want this to be just one more piece that regulators and policy makers, at both the local and federal level, take into account when they’re weighing the trade-offs. There are still clearly harms associated with legalizing cannabis, particularly for adolescents. So we’re not saying this is clear proof that it should be legalized on the federal level. But we do think it’s an important potential benefit to think about as you’re making those decisions.

Edited for length and clarity.

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