Transcript
Shelby Huffaker: Hi, everyone! My name is Shelby Huffaker. I am the chair of the San Diego Chapter of Americans for Safe Access, and today we have an exciting talk that we’re doing with Dr. Thomas Marcotte, of the Center for Medicinal Cannabis Research at UC San Diego.
Before we dive in just a little background on Americans for Safe Access. We are a national nonprofit dedicated to advancing safe access to cannabis for therapeutic use and research. So definitely follow us if you’re not already. But with that I’ll go ahead and hand it over to Dr. Marcotte would love to know a little bit about you and your background, as well as the CMCR.
Tom Marcotte: Well, thanks, Shelby. So I am a professor here in the Department of Psychiatry at the University of California, San Diego. I’ve been doing driving research for about 30 years. And I’m particularly focused on the effects of cannabis and driving over the last 10 years. I’m a neuropsychologist by training. So I’m particularly interested in cognitive functioning, real world outcomes and everyday performance.
The CMCR itself was founded back in the year 2000. So it’s probably the longest running clinical cannabis research center in the country. We came about after the passage of the Compassionate Use Act in 1996.
Senator John Vasconcellos and colleagues were interested in really enhancing the science behind using cannabis for various medical conditions. And so they funded our center here in San Diego, and we conducted a number of pilot studies, proof of concept studies looking at things such as neuropathic pain and spasticity associated with multiple sclerosis. These were small studies about 30 people, each all using THC, because that was the focus back then, and basically found that there were beneficial effects in all the conditions that were examined.
Over the years we’ve garnered funding from NIH, other state funding, some philanthropy funding. And then, with the passage of Prop 64, the center received ongoing annual funding to further our mission, which in part is very much to look at the efficacy, the negative aspects of cannabis uses medicine. So ever since then we’ve been funding about 2 to 3 studies per year at various research institutions throughout California, examining effects of THC, CBD, terpenes, etc, on various medical conditions, as well as some of the research I do, looking at potential negative outcomes relating to driving performance.
Shelby Huffaker: Interesting. Yeah. And when I was applying to graduate schools, the CMCR was a big draw for me, because I did see that, you know, there was more of a balanced focus, I think, looking at both the positives and some of the negatives as well.
And so my understanding is that you have a recent study that you are you know, talking about and getting the word about. Would you care to tell us a little bit about that?
Tom Marcotte: Sure. So we completed a study by far the largest randomized clinical trial looking at the effects of cannabis on driving performance. In our case we were looking at driving simulator performance. We recruited 191 individuals who were regular users, as infrequent as 4 times a month up to daily and multiple times a day and randomized them to smoke either a placebo cigarette, which is a THC cigarette, a regular cannabis cigarette with the THC removed, a 5.9% or 13.4% cigarette. These were all from the National Institute on Drug Abuse, which is the only at the time legal access that we had to cannabis that could then be used in federally compliant studies.
Anyway, we randomized people to those conditions. They came in. They drove the simulator. They then smoked, and we followed them over the next 4 and a half hours to see how their driving performance looked to look at the measures of blood, THC concentrations, oral fluid, and so forth. And we also did some field sobriety tests with law enforcement as well.
So I can go on. Some of the key findings were that when you take this large group of people, not everyone became significantly impaired after using cannabis. It’s hard to determine what is impairment on an experimental measure. But we estimated, based upon the placebo performance, that about 45% of the people in the THC condition would be called impaired on the simulator. The others were performing in about the same range as the placebo group.
So that could depend on how much they decided to get high and into their system. Obviously it also may relate to driving being an overlearned behavior. People do it repeatedly. I know some people say they do better while high. And you know that’s debatable. We don’t have any good evidence of that. Some people feel they’re more focused if they may be high. The challenge there is that really, when you’re driving, you want situational awareness, you want to see everything around you and take it all in and not just be focused straight ahead. But there’s no good research demonstrating one way or another whether a subset of people do better.
So that was one of the the first primary outcomes is that about half the people became impaired. The other thing we looked at was the time course of impairment, and people as a group did worse at about 30 min, about 90 min post smoking, and then by 3 and a half hours it was starting to wear off. It was marginally, statistically significant. Then by 4 and a half hours again with one cigarette people were back to baseline. So the time period was about 3 and a half, 4 and a half hours, and those people became impaired.
A key thing to know for users or people who use cannabis is that about half the people thought at about 30 min they were too high. They would not drive. That dropped down to about 30% at the 90 min point, and so forth. And the concerning part is that in about an hour and a half a lot of people felt it was wearing off in terms of the impairing aspects, and they felt okay to drive. However objectively measured, on the simulator. They were doing about the same as they were doing at 30 min. So it’s important for people to keep in mind that you may not always be the best judge of whether you’re impaired, and that sometimes, just psychologically, etc. We start feeling it wearing off and before. In fact, the effects are wearing off on how we do.
And I guess the one other — there are many important aspects from the study — one other thing I’ll point out is that we looked at tolerance, and we found that the regular users got more THC into their system after they smoked, so they were told to smoke as they would at home to get high so they could decide how high they wanted to be, and the people who are regular users got significantly higher THC concentrations into their blood, and did no worse than the less frequent users who had lower THC concentrations. So people had behavioral tolerance. They actually adjusted to the amount of THC. And we’re doing no worse than other people with lower concentrations at the same time they did no better.
So when people were told to smoke as you would to get high, choose their own level of highness, they offset this tolerance by getting more THC into their system and then driving just as poorly on the simulator. So a person could be a regular user may believe that they can handle more THC than an infrequent user. And that’s true. But if they then seek out a level of highness, it’s possible that they become sort of equally impaired.
Now, there may be other aspects we didn’t capture in the simulator. People may have a little better awareness of how to compensate in the real world for that. You know, people drive more slowly, which may or may not be safer, but at least on our simulator. We were not seeing any better performance in regular users.
Shelby Huffaker: Wow, yeah, lots to dig into there. Very interesting. So sounds like — and correct me if I’m getting this wrong — but kind of the the takeaways are that level of impairment doesn’t necessarily, doesn’t necessarily correspond with someone’s blood alcohol — or, not blood alcohol — but THC blood levels. Is that right?
Tom Marcotte: That is very true. I didn’t comment on that, but it’s been shown in other studies. Ours, perhaps, was one of the more compelling because we had 128 people who actually received active THC, and when we look at the correlation between THC concentration in their blood, right after they smoke, which is sort of the peak time and driving performance. The correlation was flat. There was no correlation at that point. And so you really can’t measure necessarily whether or not someone’s impaired by the THC in their blood.
So yeah, another study has shown so you can have someone, and it drops precipitously. So it drops within the 1st hour or so. About 90% of the THC is out of the blood, and it’s gone to the brain. It’s gone to the liver. It’s gone to other locations. So you can have someone who has a low concentration has not used in a day. A low concentration in their blood is not used in a day, and they’re not impaired at all, and it still shows up in a blood test.
But you can also have people who have low concentrations that use an hour and a half or 2 ago, and may have impairment. So it just really does not work well and does not work at all the way it does with alcohol, since alcohol is a much more linear relationship in terms of how it’s removed from the body, whereas THC just gets out of the blood very quickly.
Shelby Huffaker: Yeah, so it sounds like we need some better metrics for assessing actual impairment, since some people are more affected than others seems also very clear to be cautious, and when you do feel you’re ready to return to to driving, to be cautious of your actual feelings and wait that full 4 and a half hours. And what are some of the future research directions that have emerged from this study?
Tom Marcotte: So one thing I will comment on when it comes to tolerance. One thing we don’t know a lot about is if someone uses it medicinally. They use the same amount or dosage every day, and they’re not seeking the high. Whether or not when you develop that tolerance, you know. Now you’re okay to drive, because you’re not seeking out impairment, etc. But that’s not been well studied. We had a study quite a while ago, looking at MS spasticity in one of our earlier studies, and we showed that people who used 4% THC for spasticity did worse on the driving simulator, not surviving not surprising.
But the people who showed the most improvement in their spasticity did the least worse. If that makes sense on the simulator. So there’s some indication that if you’re focusing on symptoms and symptom relief and not trying to get high, there may be some sweet spot where you can get rid of neuropathic pain, for example, and not be at increased risk driving on the road. But there’s no no good studies really examining that component. So it’s just important to keep in mind if someone just sort of regularly doses and is not seeking a certain cognitive effect of cannabis.
So in terms of future directions, again, this is focused on my driving research. We’re very interested in the impact of high THC concentrates. So I know they’re not used much medicinally. But people often are medicinal users and occasional recreational users, or they know people who use recreationally or adult use. And there’s not a lot known about the effects of the high THC concentrates. Some people have looked at the cognitive effects. We know that in the blood people get very high THC concentrations in the blood, but then it drops very quickly. But there have not been a lot of studies looking at driving performance.
So we’re starting a study right now, if any of your listeners are interested in participating of people who either use do vaping of high THC concentrates or do dabbing. And since those are federally legal, we can’t really get those from the federal government to be compliant with federal law. We’re going to have people purchase them from a dispensary, or they’ll purchase a normal product. And then they’ll use them at home like they normally would. And we’ll actually take a mobile assessment laboratory. This is a van where we’ve put the full size simulator into the van and go to their home, and just like we did in the smoke study, follow them over the course of a number of hours, and see what if any, of the effects are on driving performance, and how that does or does not relate to blood concentrations and so forth.
So there’s a lot of unexplored territory people have looked at. Edibles, for example, have often used Dronabinol, which is the FDA-approved THC, and we’re also putting in grants to look at the effect of edibles purchased from dispensaries so real world products, how those affect driving performance.
Shelby Huffaker: And if someone was interested in joining the study, how could they find out more information?
Tom Marcotte: So I’d recommend they go to our website at cmcr.ucsd.edu. You’ll get a lot of information on our studies results. There’s some very good podcasts that our director, Igor Grant, has done with pioneers in the field about what’s the current status of medicinal cannabis research and cannabis research in general. And when you go there there’s a listing of studies and that will help you get in contact with our research center. And people can go through the screening process and see if they qualify.
Shelby Huffaker: Perfect. And yeah, we’ll definitely link that in the the final notes.
And so you know, tying everything together, curious to know how you see the CMCR’s research goals and directions aligning with Americans for Safe Access’s mission of advancing safe access to cannabis for therapeutic use and research.
Tom Marcotte: Yeah. Well, obviously, as a research center and state funded, you know, we don’t have much influence on access. But we do have influence, perhaps on policy and scientific and policymaker understanding to the effects of cannabis. So you know, our goal is to really understand as best we can in the sound scientific manner the effects that THC, CBD, we have studies now looking at terpenes may have on medical conditions and really help get that information out to the public, so they can be informed with respect to that. We also have a state funded reference lab that works with the Department of Cannabis Control — the state — to evaluate products and make sure they’re as labeled. And do they have contaminants, such as pesticides, etc, to make sure that people who use dispensary purchase products are getting safe products and getting something that is accurate in terms of the labeling of that.
So you know, we’re we’re as you commented earlier, we’re very much neutral in terms of the outcome. We just want good science, and if there are benefits we want those to be seen, and if there are some downsides or negative consequences. We also want those to be known as well.
Shelby Huffaker: Absolutely. Yeah. I think those are all important directions, and I’ll plug in too, you know, people who know me know that I’m a bit of a transit enthusiast. And one thing, I think it’s really important that we look at metrics for determining impairment, and of course, discouraging intoxicated driving. But one idea, potential idea if you’d be interested in exploring, is some of the other kind of social and structural factors that might influence whether people choose to be more safe in how they consume. A lot of cannabis businesses in San Diego and the state are zoned in very industrial areas. So what is the impact of location and and walkability? If they’re near someone’s house or workplace does that have any influence on rates of intoxicated driving? I know that they have some pretty, fascinating sort of developments in the realm of geographic information spaces. GIS, I think it’s called. So I would love to see some research, not necessarily from CMCR, but yeah. Would love to see some —
Tom Marcotte: Yeah, no, I completely agree.
Shelby Huffaker: — of that.
Tom Marcotte: Yeah, it’s a fascinating question. We just completed a large, a couple large surveys, one of 5,000 people who use cannabis in California, and we’ve had a lot of publications coming out in the last month or 2, and also a large study looking at the AAA Foundation looking at different states that legalize or have not legalized cannabis. And looking at, you know, how people decide whether or not they’re going to drive after use. And academically, you always think, oh, it’s based on whether they’re impaired or not. But there’s many other factors that go into it right? Do you have to get the job? Do you have to run an errand? You have to, you know. So there are a lot of factors that people consider when they decide if they’re going to actually get behind the wheel of a car and drive.
And we also have a a publication we’re just finishing up looking at — we asked people 2 weeks before they were going to be on the simulator, whether or not it would impair their performance. And we’re looking at how well people predicted how it would affect them, and that has ramifications in terms of planning ahead, you know. Am I just going to go to a party, or go to a friend’s house, or go to some events, and if I think I’m going to be impaired or not impaired, will that change my approach towards using ride sharing, or some other approach. So yeah, we’re trying to get to those aspects. But certainly there are structural and societal things that are problematic in terms of actually access for people. I know there’s these sort of dispensary deserts throughout California that are are very challenging for folks.
Shelby Huffaker: Yes, absolutely. Well, thank you so much, Dr. Marcotte. Really appreciate you taking the time to talk to us today. Any final thoughts for us before we let you go?
Tom Marcotte: No, I think that covers it. I think I’ll just say that people have an interest in research and science have a real chance to make an impact. It takes time because you have to come, whether it’s to our center or someplace else and participate in these projects. But people do to get some compensation for their time and effort, and how people who have an interest in this area will help become a part of the effort to really better understand the effects of medicinal cannabis.
Shelby Huffaker: That’s the goal. Alright. Well, thank you.
Tom Marcotte: Okay, thank you, and thank you for having me.
Shelby Huffaker: Absolutely.
