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Cannabis: Health effects and regulatory issues

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The legalization of cannabis in some U.S. states has highlighted the importance of understanding the substance’s health effects. At SciLine’s media briefing, three experts discussed what is known, based on scientific research, about the effects of cannabis use on human health, including its therapeutic potential, its short- and long-term health impacts, and consequences of its use by adolescents. The briefing also covered how the evolving regulatory landscape may be changing cannabis usage trends and affecting markets for other substances.

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RICK WEISS: Thank you, Josh. And hello, everyone, and welcome to SciLine’s media briefing on cannabis and health. For those not familiar with SciLine, we’re a philanthropically funded, editorially independent, free service for journalists and scientists based at the nonprofit American Association for the Advancement of Science. Our mission is simple. It’s to help reporters get more scientifically validated evidence into your news stories – not just stories about science, but any story that can be strengthened with a little bit of extra science. And in our biased view, that’s just about every story you can think of. Among other things, we offer a free matching service that helps connect you to scientists who are deeply knowledgeable and excellent communicators on deadline as needed. You just need to go to our website,, and click on I Need An Expert, and we’ll be in touch within minutes to help you out.

Today’s briefing features three such experts on a topic that’s timely for a number of reasons, including that more and more states are decriminalizing cannabis, with a number of implications for personal and public health. Our panelists today are going to talk about what the science says on this topic and help you untangle some of what you’ve heard or read so you can base your stories on the best and most recent scientific evidence. I’m not going to take the time now to give full introductions. Our experts’ bios are on the website. But I will say that we will hear first from Dr. Ziva Cooper of UCLA, who will give a brief overview of cannabis, what we know about its therapeutic potential, its possible adverse health effects in adults, including some insights, I think, into why the research is so difficult to conduct and a little bit that we’re starting to learn about cannabis during the COVID-19 pandemic.

Next, we’re going to hear from Dr. Madeline Meier from Arizona State University, who will focus on what’s becoming known about some of the mental, physical and cognitive health consequences of cannabis use in adolescents and young adults. And third, we’ll hear from Dr. Rosalie Pacula of the University of Southern California, who will focus on the regulation of cannabis and how the heterogeneous decriminalization process that’s going on across the country right now and the resulting economic and market impacts of all of that have been affecting consumption of cannabis and other substances and the public health implications of that. And so with that, let’s just get started. And, Ziva, over to you.


Cannabis: Cure or cause for concern?


ZIVA COOPER: Rick, thank you so much for that wonderful introduction. It’s wonderful to be here today. So I’m going to go ahead. And today, I’ll be talking about the evidence of the therapeutic effects for cannabis and cannabinoids as well as the known adverse effects as well. So before we talk about that, I first want to talk about what cannabis is because I think it’s important for that to lay the groundwork when we think about the therapeutic effects and adverse effects of this plant and the chemicals in this plant. So this plant has around 140 unique constituents, and these are called phytocannabinoids, that are of interest to a lot of people with respect to the therapeutic effects. We know most about these two phytocannabinoids – delta-9-tetrahydrocannabinol, which is frequently called THC, and cannabidiol, called CBD. Both of these phytocannabinoids have been tested in animals and humans for both the adverse and therapeutic effects.

We know that THC does have some therapeutic effects, but we also know that that is the chemical that is responsible for the intoxicating effects of the cannabis plant. CBD – we are starting to learn more about this chemical in humans. And what’s unique about CBD is that although it is psychoactive, so we think that it’s helpful for some indications for the central nervous system and in the brain, like anxiety, perhaps pain, it is not intoxicating. So it’s different than THC on that respect. We’re hearing a lot about some other phytocannabinoids – cannabinol, cannabigerol and cannabidivarin and many others right now. For the most part, most of these phytocannabinoids, although they’re being sold in dispensaries, have only really been looked at in animals thus far. So while there are hypothesized therapeutic effects of these phytocannabinoids, they have yet to be shown in humans. In addition to these phytocannabinoids, there are chemicals called terpenes. There’s hundreds of terpenes in this plant, and terpenes are also present in many other plants and fruits and vegetables. And it’s thought that these terpenes might also have therapeutic effects. Some of these hypothesized therapeutic effects are highlighted on this slide. For the most part, these terpenes have really only been tested thus far in animals, although they are being marketed in products across the United States.

So how are people using cannabis and cannabinoids? Some interesting trends that we’re seeing emerge that are important when we think about the public health impact of cannabis and cannabinoids is the rising THC concentration of the cannabis that has been available and has been seized and tested. And this is a figure that was published five years ago already, and it demonstrates the THC percent on the Y axis, which demonstrates the strength of the cannabis, and the year on the X axis. And what you can see is that this is unregulated cannabis – what we some people call black market cannabis – and you can see that from 1995 to 2014, the THC content rose considerably. And if you look even further in the future, we are continuing to see this rise. And in many dispensaries, while the unregulated cannabis that’s been seized here the THC goes up to 14%, in many cannabis dispensaries, you can get cannabis that has up to 30% THC. So we know there’s rising THC concentrations in the cannabis available. We know that people are using cannabis in many different ways. People are smoking cannabis. People are using it topically. They’re vaporizing it, so they’re heating it up so that it doesn’t combust. Rather, it aerosolized or vaporizes, and they inhale that vapor. And people are using it orally – through beverages, baked goods, tinctures, pills. And traditionally, it was only really products that had THC in it that was being used orally or topically or smoked, but now we know that there’s an interest in these other cannabinoids, like CBD, CBG, CBX, Y, Z – and also terpenes. So you can get these products that have different terpenes and different cannabinoids. So there’s a range of products that people are using. We also know that there’s shifting demographics of cannabis users.

We see that there’s increased use in high school students. We see their increased use in women and pregnant women as well as older adults. What about the impact of COVID-19 on cannabis use? So we did a U.S.-based survey where we asked people who had used either CBD products or cannabis products over the last year, and we received over 1,800 responses in the span of a week. It was a very popular survey. And what we found that – in general, we found that medical use increased during COVID-19, and this is an example of the increase. It wasn’t a huge increase, but we found that out of the 600 people that were using cannabis for medical purposes, about 5% increased their use to daily use during the COVID pandemic. Before the pandemic, three months before the pandemic, people who were using medical cannabis, about 25% of them were now reporting that they were either using weekly or daily for medical purposes. Anxiety was one of the most prevalent issues, medical issues that were coming up. We had about 240 people reporting that they were using cannabis for anxiety both before and during. And what we found is that there was a increased use specifically for anxiety during the COVID pandemic. We saw a very similar trend for nonmedical use, where the general increase in frequency was observed. So daily use increased from 21% to 24% Not a huge number of increase, but people were using more over the COVID pandemic. And 24% of people who hadn’t used before the pandemic were now reporting weekly to daily use.

We did not find any changes in mode of administration, so people who were smoking before the pandemic were continuing to smoke. People who were using orally were continuing to use orally. And we’re also looking at how other substance use was impacted during this period. So we have changing policy and public perception, emerging cannabis trends, shifting patterns of use in demographics. There’s clearly an urgent need to know the positive and negative health effects. So what evidence do we have for the therapeutic effects of cannabis and cannabinoids? And I’ll quickly just go through some conclusions based off of the National Academy of Sciences, where we looked at the evidence based off of placebo-controlled procedures for 20 indications where you can get cannabis across the United States. And we found that – where there were three indications for which there was strong evidence. There was also strong evidence for chronic pain. And we found some signals for other indications, such as addiction, anxiety and schizophrenia. Now, overwhelmingly, the number of studies were not done with the cannabis plant, and none of the studies were done with dispensary products.

So we have very little knowledge about the whole cannabis plant and what people are using. And I’m going to just briefly go over about cannabis as a cause for concern because I think that Madeline Meier will be talking about some of this. We know that cannabis smoking is associated with frequent bronchitis, vehicle crashes, low birth weight in mothers who are using cannabis. There’s associations between cannabis and mental health risks, impaired learning, memory and attention. We know that there can be drug-drug interactions between medical use of cannabis products and other frequently used products, frequently used medicines. And also, an adverse impact is that frequently, we don’t know what is in the bottle of these dispensary products. So we have a rapid industry growth, novel products, new ways to use, many people using. We know there is a signal for the therapeutic benefit of these chemicals in the cannabis plant, but we also know there are adverse effects, and there’s a lot of unknowns with respect to the safety and effectiveness of these products. So these are significant times for cannabis and cannabinoid research policy and health, and it is really important for us to delve into the research and also as journalists be able to disseminate what we know and what we don’t know and what the health risks are. And I welcome you to look at our website, where we are trying to do this research as well as educate the public. Thank you very much.


RICK WEISS: Fantastic intro. Thank you, Ziva. On to Madeline.

Adverse effects: Acute cannabis intoxication and long-term cannabis use


MADELINE MEIER: OK. All right. So today, I’m going to talk about the adverse effects of acute cannabis intoxication and long-term cannabis use, and I’m going to focus on cognition, mental health and physical health. So first, what do we know? We know from cannabis administration studies, which are studies that bring people into the lab and have them smoke cannabis, that acute cannabis intoxication causes transient cognitive impairment, motor impairment, psychotic-like experiences, which are things like hearing or seeing things that aren’t really there. And at higher doses, it causes anxiety. And as Dr. Cooper said, these effects are caused by the THC – right? – the psychoactive – main psychoactive constituent of cannabis. What’s interesting is there is some – it’s early days yet, but some evidence suggesting that cannabidiol, or CBD, which is another constituent of cannabis, might attenuate some of the psychological effects of THC. We also know that outside of the lab, cannabis intoxication has real-world implications, right? So if you are driving while intoxicated, you’re more likely to get in a traffic accident than if you’re not intoxicated.

We’ve also seen an uptick in emergency department visits for cannabis-related mental health emergencies. We also know from naturalistic studies – these are studies that recruit cannabis users and nonusers and compare them on outcomes – that heavy – long-term heavy cannabis users show more IQ decline compared with nonusers, more learning, memory and attention problems. They also sometimes show brain differences – for example, lower regional brain volume in some studies – but this is somewhat inconsistent. And long-term cannabis users show more mental health problems, including depression, suicide and psychosis. What’s interesting is that in general, with a few exceptions, we don’t see clear and consistent evidence that long-term cannabis users show physical health problems. So these are data from the longitudinal Dunedin study, which is a study of a thousand people followed from birth to midlife. And what this is showing you is risk of a number of physical health problems as a function of duration of cannabis use. So here we have risk of COPD, or chronic obstructive pulmonary disease, high systemic inflammation, metabolic syndrome, which is a cluster of conditions that increase your risk for things like heart attack, stroke and Type 2 diabetes, obesity and periodontal disease, or gum disease. And we’re plotting that as a function of duration of cannabis use.

So here in green, we have lifelong cannabis nonusers, in blue cannabis users who used fewer than five years, in yellow between five to nine years, and in orange between 10 to 14 years, and then in red those who used 15 or more years. And again, what you see is that the long-term cannabis users were not generally at higher risk of these physical health problems compared with shorter-term cannabis users and nonusers. The one exception here was for periodontal disease, or gum disease. The long-term cannabis users were at higher risk. It’s sort of interesting that there’s some evidence that long-term cannabis users actually have lower risk of obesity. Now, like I said, we didn’t look at this in this study, but there are some exceptions here. So one exception is other researchers have shown that cannabis users are at heightened risk of heart attack and stroke in the hours following cannabis use. And then if you recall back in 2019, there was evidence that there was evidence that marijuana vaping was causing lung injury, and that seemed to be marijuana vaped from the black market. So there are some exceptions here to physical health problems.

What we don’t know – what I’ve talked about thus far sort of is across the board. It’s not asking, you know, are these effects different for adolescent users or adult users? But when we do ask that question – are adolescents more vulnerable than adults? – what do we find? And in general, this question comes from a theory that because adolescents’ brains are still developing, adolescents may be particularly sensitive to the effects of cannabis and then at higher risk for negative cannabis-related outcomes. And there’s actually some evidence from animal studies about this, right? They can dose adolescent animals and compare them to adult animals. And some studies find that the adolescents fare worse. Much harder to do this kind of work in humans, right? We can’t ethically dose adolescents and human adults on the off chance that there might be some negative effects of cannabis. That said, from naturalistic studies, there is evidence that earlier-onset youth – so the younger you start using cannabis, the higher risk of negative outcome.

Now, that research is a little bit hard to disentangle, right? So is this the case that the earlier onset use is because, you know, you’re using in adolescence, when your brain is sensitive? Or is the earlier onset use really just an indication of a longer duration of use? And so that’s difficult to disentangle. In general, very few studies have actually compared adolescent-onset users with adult-onset users. And one exception to this is a study that we did back in 2012. Again, these are data from the Dunedin study, which is that study of a thousand people followed from birth to midlife. And in this study, we assessed people’s IQ in childhood, before any of them began using cannabis, and then again assessed their IQ in adulthood after some members of the study had begun using cannabis for many years. And I’m showing you here data about change in IQ from childhood to adulthood as a function of duration of cannabis use over time. So here are our short-term users, medium users and long-term users.

And I’m plotting that for users who started using cannabis in adolescence before age 18 and then people who started using in adulthood after age 18. And what you see here in the maroon bars are the associations between long-term cannabis use and IQ decline for the adolescent-onset users. So this maroon bar shows that, you know, as these adolescent users continue to use for more and more years, they showed more and more IQ decline. So these long-term, kind of persistent adolescent-onset users lost about eight IQ points from childhood to adulthood. What we see here for the adult-onset users in the orange bars – we did not see that association, suggesting that adolescents are more vulnerable. Now, I’m often asked, well, what does this eight-point IQ decline actually mean? And so what you can do is sort of think about a person with an average IQ – so someone who is in the 50th percentile for intelligence, which means out of a hundred people, they have higher IQ than 50 and lower IQ than the other 50. Well, you take someone with average IQ, and they lose eight IQ points, that actually drops them from the 50th percentile down to the 29th, OK? What I want to note – something that often gets lost in the media as well as other journal articles – is that we did not see evidence of IQ decline – much IQ decline in the adolescent-onset short-term cannabis users, right? So those adolescents who used just short term in adolescence lost only about three IQ points.

Does quitting help? Again, this question is hard to answer because of the lack of research. But there is some evidence suggesting that, yes, quitting can help. I’m taking this information from studies that follow cannabis users from before to a few weeks after they quit. And those studies show that some cognitive functions might improve after quitting. There’s also evidence that if a person reduces their cannabis use, they might show decreases in depression symptoms. But again, there’s really just too few studies using this kind of stronger methodological design where you’re following people from before to well after cessation. Finally, if our association is causal – well, yes, in terms of the laboratory studies, right? When we go and we give people cannabis in the lab, we know that the THC is causing the adverse effects. But in naturalistic studies – these are studies that cannot conclusively demonstrate causality, right? There are so many possible alternative explanations, it’s hard to rule them all out. But we can strengthen the evidence for causal inference by ruling out some of the most obvious alternative explanations. For example, which came first, the cannabis or the negative health outcome? And we did that, for example, in our study of IQ, right?

We showed that cannabis users did not have lower IQ to begin with. We also take account of other substance use. You know, is the IQ loss associated with cannabis, or is it really the fact that cannabis users are using other substances? And so this is important to evaluate in, you know, studies that are coming out. How well did they address alternative explanations? The other thing we can do is test for a dose-response association – right? – because if you see that, you know, more cannabis use is associated with higher risk of negative outcomes, that’s where it’s fundamentally necessary in order for there to be a causal influence. Some things I didn’t get to discuss because of limited time are risk for cannabis dependence, effects on fetal development and then differences between medical and nonmedical users, but I’m happy to answer questions about that. Thank you for your time.


RICK WEISS: Super interesting. Thank you, Madeline. And we will jump here to Rosalie Pacula.

Regulation of legal cannabis in the United States


ROSALIE PACULA: Thank you so much, Rick. And it’s really lovely to be following both of the previous speakers, who are incredibly knowledgeable on the health effects and the cognitive effects of cannabis. And a point that both speakers have already made – it’s really important to reiterate – is that we’re talking about cannabis as if it’s a single product. And as Dr. Cooper clearly articulated, cannabis is a very complex plant that has actually changed a lot over time as we, both scientists as well as farmers, have learned quite a bit about the plant and what consumers like about the plant. And it’s been engineered to have different attributes. And so one of the things that I try to emphasize when we – when people ask about legalization policies – the state policies, and now we are having a national discussion about legalization in the U.S. – is to think about what we’ve learned about the plant and its properties, and what are the appropriate regulations to think about in those circumstances?

So first, I want to emphasize that thus far, the states that have already regulated cannabis for adult use, or often referred to as recreational purposes, have done so treating cannabis as more of a commercial enterprise of a relatively innocuous good because there hasn’t been clear science showing demonstrated significant reason to suggest that this is a dangerous substance. And as such, much of this regulation is focused on licensing, location of stores, hours of operation at the local level, whether the laws will allow on-site consumption or the sale of other products. Testing is done, but it’s largely for mold and pesticides, things that State Department of Agricultural Agencies (ph) are well aware of that should be thought of, but not perhaps things that are done as systematically by the FDA when a product is nationalized. And taxation has largely been based off of the sale of volume of the good instead of on the major ingredients within the cannabis plant, which, as Dr. Cooper emphasized, is not homogeneous across all plants. And the potentially negative attributes of the plant are – tend to be tied to certain elements more so than others. Public health perspective for regulation, which I believe is seriously needed when we think about legalization, needs to think about regulations from a slightly different perspective. And we’re seeing more of that when it comes to edibles because, perhaps, this is where we immediately saw some harmful effects associated with naive use.

When it comes to edibles, states are being much more careful about testing of edibles, requiring certain processes for their production, ensuring that a single dose, a 10-milligram dose, which is a standard that the industry has basically set, is easily demarked so that a user doesn’t mistakenly overconsume. Packaging elements are done on it. And in some states, they’re requiring the edible products, even when they’re unwrapped, to have some sort of stamping so that you can determine when a gummy is, in fact, a THC-imbued gummy versus a regular candy gummy available at your local candy store. These are examples of more public-health-minded regulations that we aren’t seeing with respect to other cannabis goods and are dramatically needed. I’m going to highlight five key health regulations that I think are not considered carefully enough in current state legislation and regulation and need to be considered when we go to a national debate about it. And let me just say quickly what they are – restrictions on the ingredients and extractions allowed from the plant itself, restrictions on the amount sold, taxing potency of the plant or THC rather than the amount sold, the need for funding and conducting reliable and random compliance checks and regulating advertising and promotions. These are all things that we pay careful attention to when we’re talking about tobacco and alcohol in our state regulations and are things that are often not as carefully addressed in cannabis regulations thus far.

So first, restrictions on ingredients and extractions allowed from the plant. None of the current state laws that have legalized cannabis impose any sort of caps on the potency of the plant that is sold. And as was shown earlier by Dr. Cooper, the average potency – and that was of illegally confiscated cannabis – has been rising over time. Cannabis sold within the state of Washington in 2019 had – the plant material, the buds and the flowers – had an average potency of 21% THC. And this is the delta-9-THC, the ingredient that Dr. Cooper mentioned is the main psychoactive ingredient. This is the largest category of cannabis products sold, but it is no – it is falling; it has stabilized. The biggest and fastest-growing segment of the cannabis market is in concentrates, where the average potency of the concentrate sold is 70% THC. So when we talk about people using cannabis and we talk about how much cannabis do they use, it’s not just enough to know, did you use cannabis, but we need to know what product did they use to better understand that dose that Dr. Meier was talking about and to correlate that with a outcome.

Every state since late – well, I shouldn’t say that. Every state has allowed any product to be sold because of the concern about the black market. Since legalization, though, several states have tried to impose a potency cap because of the harmful acute effects that have been discovered by naive users using these products. And unfortunately, with the exception of edibles, most of these caps have failed, whether they’ve been set too low and the industry has countered them or the argument is made that just placing a cap will encourage the black market. This is a really important point I hope we can come back to. It’s also important to know that the plants themselves are grown, but it’s not necessarily the plant that is harmful. It’s the extracts that can be taken from the plant and mixed with other things. It’s well-known, as already stated, that delta-9-THC is the main psychoactive ingredient of what people largely refer to as cannabis, but what we’re finding now since the 2018 farm bill is that industrial hemp, which on average has less than 0.3% delta-9-THC, can be used to extract delta-8-THC, which is a alternative psychoactive ingredient that is being shown to have some of the same psychoactive responses as delta-9. Delta-8-THC – part of hemp that’s extracted from the hemp plant – is legal, while delta-9 is not.

The inconsistencies in our treatment of the potentially psychoactive component of the plant is something that needs to be considered. And, of course, there’s a concern about additives, as was mentioned already about the concerns of the EVALI case. It was believed that it was vitamin E acetate that was added to vaping cartridges perceived to be in the black market that was causing the most significant lung injury. And the problem is that we didn’t have a system to verify whether or not vitamin E acetate was being added to legal cannabis because there was no FDA regulation of these vaping cannabis products. So understanding additives and regulating and making them clearly known to consumers is an important part of any public-health-oriented regulation. We need to think about restrictions on amounts sold. And the reason why I say that is the current sales limits that states have in place are based on amounts – most common between 1 and 2.5 ounces of flower people can buy in a single purchase or up to – between 5 and 15 grams of concentrates. And these sound like really small, innocuous amounts. The problem is that because the potency of cannabis varies so substantially across products, the actual amount of THC that an individual can purchase with these sales limits that by volume look like they’re relatively innocuous can actually be quite substantial. In a study that we just had published in the American Journal of Preventive Medicine, we show that at average potency products, all states allow the purchase of up to 510 milligram doses of THC in a single purchase.

So a person can go in and get 500 doses of THC, can put it in the car, come back in and buy another 500 doses of THC. Why is this a concern? Public health advocates are concerned because of the amount of THC that can be purchased, but everyone should be concerned because this is an easy avenue for diversion to the black market from legal stores. Few states tax THC, but instead base their tax on the sales price or the average volume sold. And what I’m showing you here is data from the state of Colorado produced by the Department of Revenue that shows that the average price per dose of THC has actually been declining during legalization. The solid bar screen (ph) is adult average price per concentrate, TH dose of concentrate. The blue bar is that for flower. The gray bar is for edibles. The dots show the medical market because medical market is not taxed at the same price as the recreational market. And basically, what you’re seeing is the price per dose of THC is falling significantly over time. Why does this matter? When we think about alcohol and the potential harms of alcohol, we tend to tax alcohol based off of the ethanol content in alcohol. Why? Because higher ethanol content increases impairment and intoxication and is more highly associated with health harms and violence. In the case of cannabis, we believe higher potency THC is what’s likely correlated with the significant health harms or even impairment for driving. And if we don’t price and tax based off of THC, we’re treating low-dose THC, or the analogous of wine and beer, the same as high-potency THC, the analogous being vodka or 100% proof alcohol.

These important differences matter. State regulations need to include random compliance checks. This is a standard way that we can ensure that unlicensed stores do not pop up and licensed stores are complying with the rules that are set with regard to sales to minors, free giveaways, restrictions on on-premise consumption or sale with other goods that they are not allowed to be selling with. This has been a very important tool in the strategy to combat sales to minors for alcohol and tobacco. It’s not being used for cannabis. And finally, regulation of advertising and promotion is very important. The cannabis industry is doing a very good job of promoting itself in ways that are – not been allowed for alcohol and tobacco, whether it’s advertising the huge, significant revenue that they can provide to state coffers at a point where state coffers are strapped – COVID-19 – whether it’s talking about the relative safety of cannabis vis-a-vis other intoxicants or whether they’re talking about how it can help solve a major crisis – in this case, the opioid crisis. These are all actual advertisements placed by the industry. And the products are showing up everywhere in forms that are not supposed to be or not in the spirit of the state regulations, whether it’s cannabis-infused wine that’s nonalcoholic, candies that look like other legitimate candy products or even ice cream.

So industry is capturing the regulation because of the perception that cannabis is a single good and it’s relatively harmless. And because of this, positive scientific results that reinforce that are being used immediately in the promotion of their good. And the time that it takes for science to robustly investigate is not being allowed. And so we’re behind the game when it comes to the science. Ways people are being exposed is positive messaging, and it’s becoming normalized before we actually know what the true implications are. And the impacts of that is national, not just in the places where the cannabis has already been legalized. With that premise, it’s going to be very difficult to establish clinically appropriate regulations on things like potency once the industry has already taken place because it’s – as we are seeing in states right now – Colorado, Washington, even Massachusetts – efforts to try to change the potency of products once you have the legal market are met with very significant – what’s the word? – resistance. And I’ll stop there.


What are some science-backed tips and pitfalls to avoid for reporters covering cannabis?


RICK WEISS: Thank you, Rosalie. Great. OK, very interesting presentations. Let’s get started. We have a lot of questions stacked up, but I want to just quickly throw out an initial question to all three of you, which is, you know, maybe most helpful to reporters who are on this beat or trying to cover this. Give me a quick example of one thing that either you think reporters are doing well in the domain of covering the cannabis topic or that you think they could use some advice on or do a little bit better on. Just start with some professional advice here. And I’ll start with you first, Ziva Cooper.


ZIVA COOPER: Great. Thanks so much. So one thing I really appreciate when reading the popular media about cannabis and cannabinoids is when the reporter makes it a very explicit point to describe to the reader if the scientific study is being done in cells, animals or humans. I frequently see these great headlines about the therapeutic effects of cannabis only to learn that it’s happening in a cell line when I actually go to look at the paper. And I think it’s really important to keep the community and the U.S. population informed as to the fact that what’s happening in a petri dish is very different than what we expect to happen in a human. Another point that I also really appreciate is when the reporters also directly link what it is they’re talking about to the actual paper. So frequently, this does not happen, and it’s really upsetting, especially if somebody is a researcher who wants to go look at the original paper. But I imagine that for the general community, this is also really frustrating as well.


RICK WEISS: Great. Madeline.


MADELINE MEIER: Yes. I think for the work I’ve done, I’m really looking for a reporter to recognize that studies differ a lot in what they’re calling long-term frequent or heavy cannabis use. And so it’s really important that as a reporter, you take a look at the article and see how the paper has defined frequent or regular or heavy cannabis use because lots of times, we’ll see that, you know, in one study, we’re talking about 30 or more lifetime uses, and another study, we’re talking about daily use for 20 years. You can’t compare those two studies. And so it is very important for researchers to be clear about what they mean when they talk about frequent and heavy users, but also for reporters to understand that sometimes there’s differences across studies that are really important for understanding health implications.


RICK WEISS: Great. And Rosalie Pacula.


ROSALIE PACULA: Yeah, mine won’t be surprising at all. It follows very naturally on the other two, and that is paying attention to the studies, whether we know what types of products were being consumed, so that we have a sense of how much potency was involved in those products. Daily use of a low potency product is not likely to have any negative, harmful consequences in terms of psychoactive effects, whether driving impairment, work and the like, and may be very therapeutic and beneficial. Daily use of a concentrate that has an average potency of 70% THC is a different thing. So understanding that cannabis is – the reporters who emphasize that this is a heterogeneous product – and that is part of the reason why the blending of the science is not a good thing to do, and one has to be very careful in reporting it. The beer industry gets very upset when you loop their studies in with the liquor industry. They want to be known as something different ’cause they know their product has less ethanol. And I think we do better reporting the news when we are clear about the product that we’re talking about.

Are the health effects and level of impairment caused by cannabis versus alcohol comparable?


RICK WEISS: Great. I’m going to start with a few questions here. I have a few questions here that are variants on a theme of comparing marijuana to alcohol. Nancy Wartik at New York Times is asking for a way to sort of compare the impacts of those two drugs. And Carrie Poppy, freelance from California, is asking specifically for Dr. Meier – how driving on THC compares to driving drunk. Dr. Meier, maybe you could at least start with that question at both its general and specific levels.


MADELINE MEIER: Sure. So there are actually not very many studies that directly compare alcohol and cannabis. It’s something that I’m working on right now. There are a few studies that have done it. For example, data from the Dunedin study have compared long-term use of alcohol and long-term use of cannabis on outcomes like having a job as an adult or how much you get paid or how much savings you have, and they found really no differences. But this is a difficult question to answer – OK? – for a number of different reasons. And I think it’s a question that’s really important to answer because we’re seeing, you know, proponents of legalization say things like, well, alcohol is legal, and cannabis is safer than that. But really, there’s not that much research addressing those questions.


ROSALIE PACULA: If I could – speaking directly to the driving impairment, there – I actually disagree. I think that there’s been a lot of really good lab studies done, where they bring people into the lab and they give them specific doses of alcohol and/or THC, and they test their basic driving motor skills given different levels of impairment. Now, again, the amounts of THC that are being administered in the lab are significantly lower than what we are seeing in terms of products sold in the legal markets. But generally, what they’re finding is that there is mild impairment associated with cannabis use in terms of motor skills for driving. But on average, people who consume cannabis and only cannabis drive much slower because they adjust for their – the effects of the cannabis on their perception. In the case of alcohol, it’s initially (ph) the stimulant.

People tend to drive faster. But the real issue that they’re starting to uncover is that the impairment and the effects on motor skills and other skills used for driving when cannabis is used in conjunction with alcohol and alcohol levels that are below the legal limit of 0.08 – so, say, a 0.04 BAC level plus cannabis – that impairment is actually higher than alcohol alone. And so, again, it is a complex thing to study. We’re seeing in the lab that there are real negative effects of cannabis used in conjunction with alcohol that is more damaging than alcohol alone. Cannabis alone appears to be less harmful than alcohol above 0.08 levels when cannabis is administered at very low levels of THC vis-a-vis products sold in the legal market.

Does smoking marijuana adversely affect the heart and lungs as much as smoking tobacco?


RICK WEISS: OK. A couple of questions here about marijuana and/or cannabis and physical health, especially lung health. Jim Morelli of WFXT TV in Boston is asking – noting that bronchitis was mentioned as a possible health effect. Can we equate smoking marijuana regularly in terms of adverse effects to the heart and lungs with smoking tobacco, or is it safer? Abraham Ethen (ph), a freelancer, tuned in, has a similar question – if there’s any correlation with lung cancer the way cigarettes have been linked. Any of you want to pick that one up?


ZIVA COOPER: Yeah, so I can briefly touch on what we found with the National Academies of Science and Engineering (ph) report. And what we concluded – again, this was based specifically on smoking cannabis, not vaporizing, which I know is also a question that we can get into – the differences between vaporizing and smoking cannabis. What we found was that, again, there was substantial evidence supporting the fact that smoking cannabis is associated with bronchitis and some other respiratory health risks that actually get better once people stop smoking, and that’s important to note. We did not find an association between cannabis smoking and lung cancer, which is different than what you would expect to see or we have seen with smoking tobacco. And so that was a really important point. And it was actually established by a researcher at UCLA who studied this for about 25 years and came out, you know, with a hypothesis that – or came out with a conclusion that was very different than the hypothesis that he went in with, where there does not seem to be an association between smoking cannabis and lung cancer.

Now, with respect to vaporizing, frequently, people assume that vaporizing cannabis, because you’re not combusting the product, has a lower respiratory health risk than smoking. And I think one thing that’s important to distinguish is that when we’re talking about vaporizing and we think about the potentially better health profile than smoking, generally, we’re thinking about the plant product, vaporizing the plant product, not vaping those extracts, those cartridges that have additives, that have solvents of which we really don’t know anything about at this point. We also don’t know very much about the long-term effects of even vaporizing the plant. So the field is very much in its infancy, despite the fact that these products are really popular.

How does cannabis use impact traits such IQ, creativity, and compassion?


RICK WEISS: OK, question for Madeline Meier – a couple of questions here, related again. Using IQ as a measure of intelligence is, of course, limited. This is from Karen Michel, Public Radio, New York, wondering if there’s a change in creative output for, say, adults who began consuming cannabis in adolescence or other measures of significance, like compassion, for example. Also, Nicholas Gerbis of KJZZ in Phoenix – another angle on this for Dr. Meier- given some of the criticisms of the efficacy of IQ as a measure of intelligence at all, how confident are you that a three-point IQ shift either falls outside of the error bars or indicates a real shift in intelligence?


MADELINE MEIER: Wow, that’s a lot. So let me just first tackle – I hear this actually very frequently that IQ is not a great measure of intellectual functioning. And in fact, despite that kind of general perception, in our field, our measures of IQ are probably the most – one of the most psychometrically sound tests that we have. And what – so what does that mean? That means in terms of kind of reliability or, you know, kind of taking the test on one day and then retaking another day, do you get the same test result? Yes. For IQ, we do. It also means, does IQ actually matter? I mean, are we measuring what we think we’re measuring? Does it predict things in the future that we’d expect it to predict? And it does. It – very well, people with higher IQ tend to have better jobs. They make more money in their jobs. They actually even live longer. And so IQ is a very good measure of intellectual functioning or global intellectual functioning. And so I guess the next question was, well, what outside of IQ?

And you can break down cognitive functioning into more specific domains – right? – things like working memory, attention, learning. And in general, what we’re finding across studies is that we see that long-term cannabis users perform worse on those tests. In terms of creativity specifically, I often hear sort of anecdotally that, you know, cannabis increases my creativity. And I think while intoxicated people feel that way, but we – I have not personally done research on, you know, creativity while intoxicated. My – most of my research is looking at kind of longer-term effects. And so I would say that there’s not – I don’t know about creativity per se.

Is there research on the links between cannabis use and conditions such as dementia or schizophrenia?


RICK WEISS: Anyone else want to comment on that before we move on? OK. A couple of questions here – again, related – that I’ll throw together here for whoever wants to jump on it. This is from Monika Maeckle at San Antonio Report. Is there any research on cannabis use for dementia and/or research on interactions with prescription drugs? I assume that means for dementia. And related to that, Carrie Poppy, freelance from – in California, had to ask whether cannabis use for schizophrenia has been shown to either help or harm folks.


ZIVA COOPER: So I can touch on this. There’s been a lot of interest recently looking at cannabis and cannabinoids – specifically cannabinoids, the individual constituents in the cannabis plant – looking at agitation and delirium in dementia and Alzheimer’s. And some of these studies have specifically concentrated on CBD. Some of them have also concentrated on very low levels of THC. Some of these studies haven’t been published yet. In fact, many of these studies haven’t been published yet. But there is a growing literature in this respect, I think simply because of the increased population that is being diagnosed now with Alzheimer’s and dementia. With respect to schizophrenia – so there is a association between cannabis use and the development of schizophrenia. This is not a causal link, OK? It’s an association. With respect to studies that have looked at the potential for cannabinoids, those chemicals in the cannabis plant, to potentially help people with schizophrenia, those studies have really concentrated, again, on CBD cannabidiol, the nonintoxicating component of the cannabis plant, not on THC. It seems like THC is not a good thing to use if there is a increased risk for developing schizophrenia.

Has the THC content in cannabis increased, and if so, is this driven by consumer demand?


RICK WEISS: Question from Naseem Miller at The Journalist’s Resource – how is the THC content increased in cannabis, and is this increase driven by demand from consumers?


ROSALIE PACULA: Well, it’s been increasing because of new growing techniques that are being used to accentuate certain cannabinoids of the plant. There’s a whole literature on how to grow cannabis in ways that increase both THC as well as certain – it’s now a cottage industry the way wine tries to get produced to have different accents and the like. Is this driven by demand? I think that’s a great question. I can’t say that I believe the answer is yes. I think that there are certain users that are very – let me be clear. The vast majority of consumption of most intoxicating goods, whether we’re talking about alcohol, cannabis or even some of the harder substance, it’s the near-daily heavy users that are the biggest purchasers.

They purchase the largest amount of the good, even though they represent only about 20% of the total using population. This is known as the 80-20 rule. Because heavy users are the largest purchasers, the industry is inclined to try to sell enticing products to that very small but frequently buying group of users. So are they responding to demand? If you’re talking about demand for this very small group of heavy, frequently using cannabis users, the answer is yes. They’re responding to that very small group. But usually when we think about cannabis use and when – most frequently, what we’re measuring in cannabis use is not those heavy daily users who are using large quantities frequently throughout the day.

What level of cannabis use leads to adverse effects—how much is too much?


RICK WEISS: So there’s a few questions now coming in that I think are responding to something you’ve all mentioned, which is that it’s hard to say how much is too much and get some solid measures here. But Nancy Wartik at The New York Times, Lila Thulin at Smithsonian, others, I think, are getting at the same question here, which is, how much is too much? Where do you start seeing negative effects? I know that you can’t say scientifically that it’s a clean cutoff, but I wonder if just from your own experience, from your research that you’ve done, what’s the advice you can give to people about where they may be crossing a line and expecting to get negative health effects, either physically or cognitively or mental health-wise? Do any of you dare to sort of – yeah, Ziva.


ZIVA COOPER: So as a researcher who does actual drug administration studies where we compare placebo cannabis or placebo cannabis product to a range of doses, the first important thing to remember here is that tolerance or the population you’re studying is really important. So somebody who uses cannabis once a month will respond very differently than to somebody who’s using multiple times a day. So the absolute dose, it’s hard to know what to expect unless you’re also thinking about who that person is. And we’re also learning about other physiological variables that play into this – for instance, males versus females. One area of research that I hold very dear to my heart is that males and females differ with respect to their response, whether they are using once a month or many times a day. And what you can do in the laboratory is that even with these low concentrations of cannabis that are not even available in dispensaries anymore that we get from the government – so we’re talking 3%, 6% THC – when you give those products to people who aren’t seasoned, you know, cannabis users, they will tell you how high they feel, and you can look at the cognitive impairing effects in those particular people.

And you can see that the cognitive impairing effects definitely exist even at those what we think, relative to what’s available in dispensaries let’s say in California, pretty low levels. When you’re recruiting people or when you have people in the lab who are using every single day, you might not see the cognitive impacts with those high levels, but they still will report that they do feel some intoxication. So even at those low cannabis strengths, there still are psychoactive effects, including – one audience member was asking about physiological dependence. And we know that physiological dependence does occur in a subset of people, even in daily cannabis users, even when they are using very low THC concentrations. So these things are really important to consider and to think about, especially with writing scientific journal articles about cannabis – is that the individual is really important when we think about the health outcomes and health impacts of cannabis use.


MADELINE MEIER: I’ll just add that when we’re looking at sort of longer-term effects – right? – say, outside of acute intoxication – we do tend to see the negative sort of longer-term effects are concentrated among the longer-term frequent users, right? So you have higher risk of developing cannabis dependence, which is compulsive use despite experiencing problems because of your cannabis, if you’re a daily user, right? So short-term infrequent use is not nearly as problematic as long-term heavy use.


ROSALIE PACULA: And this is also why there is encouraged – there’s a need for us to try to encourage policies that offer more standardized dosing on products other than just edibles so that naive consumers, who do represent the bulk of the total population using, even if they aren’t the most frequent purchasers, are able to use the product safely and without any negative consequences.

What is one key take home message for reporters covering cannabis?


RICK WEISS: We are just about out of time, and I’m sorry we still have some questions left. But I want to wrap up by asking you each to offer a take-home point or something that you want to make sure reporters walk away with here. I’m going to just throw in one more question here that you may or may not choose to answer. This is really a journalistic ethics question that I’m going to throw at three scientists. But it’s so interesting, I’m just going to throw it out there, that – from Amanda Lichtenstein at The World, show on public radio. Do you think there’s a conflict of interest to be a cannabis user and also a journalist reporting on the cannabis industry? If that is something you’ve been thinking about and want to comment on, feel free. But I’m going to actually make my way around the rounds here to your little take-home from each of you. And I want to remind people online here today that as we wrap up today, you will get a small survey popping up. And I really would appreciate it if you could answer three quick questions. It will help us maintain a high quality for these media briefings for you. I’ll start with you, Ziva, if you’d like to wrap up.


ZIVA COOPER: Sure. So my wrap-up point – generally, my talks and the information that I give people is full of depends. We don’t know. We’ll see. Tell me – I’ll tell you in 10 years. And I just want to offer some bright horizons here. Even though public policy is outpacing science and consumer behavior, and industry is outpacing science, you know, there’s a lot of really excellent work being done, collaborative work between economists and people who are, you know, administering drugs in the lab. And this has become, I think, a golden age that has been spurred by the national interest. And, also, because we’re in this age of information, people are hungry for data and for actually knowing what is going on. And so I think that, again, in the next 10 years, we’ll know a lot more. But this is a really exciting time. And as journalists, you have a wonderful opportunity to be able to share with the public about what we know and what we don’t know and what the health risks and therapeutic potentials are.


RICK WEISS: Fantastic. Madeline Meier.


MADELINE MEIER: So my take-home message is that when we’re looking at, you know, kind of long-term negative health effects of cannabis, this is really concentrated, as you heard, among the long-term or heavier users who do not comprise the vast majority of cannabis users, which is good news, right? I think the issue is that, you know, the public perception of risk of cannabis is going down, and use may increase with increased legalization. So that’s the real concern there. In terms of the reporter’s question about ethics, I’m just going to put it right back and say, what about a researcher who uses cannabis (laughter) heavily, so?


RICK WEISS: A question no one asked, amazingly enough, whether any of you are users. I will leave that question open and move to you, Rosalie Pacula.


ROSALIE PACULA: Well, I’m not going to answer the question you just asked, Rick, but I will answer the question that was raised by the reporter. And I don’t think that there’s an – I don’t think there’s an ethical conflict at all in that. I think that this area is informed by a bunch of people’s different experiences. And that experience was something – likely provides different insights than someone who has no experience with that. But it is important to keep in mind that we’re making policy for our population. And what segment of the population does your experience reflect? So the key takeaway I have is probably not surprising to many of you, and that is that we aren’t really yet treating cannabis like alcohol and thinking about it like alcohol.

We have a large number of regulations in place for alcohol that target the at-risk and heavy drinker. We do not have the same cautions developed in our state or current discussions for national legalization to protect the typical consumer from becoming a heavy user. And so I encourage reporters to push harder when they talk to state agencies or – and regulators about what are they doing that is like alcohol, and what are they forgetting about alcohol. Look at closely how we regulate alcohol, and think of the parallels, and I think you’ll have a better mind – a better idea of what I have in mind.


RICK WEISS: Fantastic. I want to thank all three of you today for such an interesting and dynamic discussion and for providing a great example of how journalism stories about something that’s going on in society that people might not think could benefit from some injections of science can actually be so much stronger by finding out what the research says about things that are going on in culture and society. It’s just been a fantastically enriching discussion today. I want to thank you all so much. Thanks to those who are attending today. We look forward to seeing you at future SciLine media briefings. I do encourage you to follow us on Twitter – @RealSciLine. Please do fill out the very short survey at the end of this thing to help us out, and visit our website at Thanks, and we’ll see you at the next briefing.

Dr. Ziva Cooper

University of California, Los Angeles

Dr. Ziva Cooper is the director of the UCLA Cannabis Research Initiative and associate professor in the UCLA departments of psychiatry and anesthesiology.  Her research involves understanding variables that influence both the therapeutic potential and adverse effects of cannabis and cannabinoids.  Her current projects funded by the National Institutes of Health and the state of California include understanding the potential for cannabis constituents to reduce reliance on opioids, differences between men and women in their response to the pain-relieving effects of cannabis, and therapeutic effects of cannabinoids in patient populations.  Dr. Cooper served on the National Academies of Sciences Committee on the Health Effects of Cannabis that recently published a comprehensive report of the health effects of cannabis and cannabinoids.

Dr. Rosalie Liccardo Pacula

University of Southern California

Dr. Rosalie Liccardo Pacula is a professor and the Elizabeth Garrett Chair in Health Policy, Economics & Law in the Sol Price School of Public Policy at the University of Southern California. Her research focuses on issues related to illegal or imperfect markets (health care markets, insurance markets, markets for addictive goods), measurement of these markets, and impact of policies. She has applied much of this knowledge to study addiction, addiction policy, and how the health care system delivers and finances treatment for addiction services. She was the lead investigator of several National Institutes of Health studies examining the impact of cannabis liberalization policies (decriminalization, medicalization and legalization), and is currently conducting NIH-funded work evaluating the impact of cannabis liberalization policies and markets on alcohol and opioids use and harm.

Dr. Madeline Meier

Arizona State University

Dr. Madeline Meier is an associate professor in the department of psychology at Arizona State University.  Her research uses prospective longitudinal and case-control designs to understand the causes, course, and consequences of problematic substance use, primarily cannabis use. Her main interests involve understanding how cannabis use affects both mental health and physical health across the lifespan. Dr. Meier also has expertise in using retinal imaging, a tool taken from ophthalmology, to understand the vascular pathophysiology of psychosis.

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