Science Friday - Where are we with understanding the health effects of cannabis?

Episode Date: September 11, 2026

When states began legalizing recreational cannabis a couple decades ago, 25 million Americans said they used the drug. That number nearly tripled to 70 million by 2023.There are a lot of open questions about how it affects us. Why do some people find more pain relief from THC than traditional painkillers? Is it really better for sleep? What are the effects of long-term use?Host Flora Lichtman is joined by two scientists taking on these kinds of questions: Experimental psychologist Ryan Vandrey, who’s studied the health effects of cannabis for 26 years, and neuropsychologist Natasha Wade, who studies the effects of substance abuse on adolescent brains. She recently analyzed data from 11,000 teens to understand how cannabis affects development.Guests:Dr. Ryan Vandrey is an experimental psychologist and professor at the Johns Hopkins University Behavioral Pharmacology Research Unit and helps lead the Johns Hopkins Cannabis Science Lab.Dr. Natasha Wade is an associate professor in the Department of Psychiatry at UC San Diego and licensed clinical neuropsychologist.Transcript will be available after the show airs on sciencefriday.com. Subscribe to this podcast. Follow our show on Instagram, TikTok, Facebook, and Bluesky @scifri and sign up for our newsletters. Got a science question that’s keeping you up at night? Call us: 877-472-4374 Hosted by Simplecast, an AdsWizz company. See pcm.adswizz.com for information about our collection and use of personal data for advertising.

Hey, it's Flora, and you're listening to Science Friday. When states first began legalizing recreational cannabis a couple decades ago, 25 million Americans said they used the drug, according to the National Survey on Drug Use and Health. That number nearly tripled to 70 million in 2023. And there are a lot of open questions. Why do some people find more pain relief from THC than traditional pain killers? Does it really help your sleep?

what are the effects of long-term use? We have two scientists here with us who are on the forefront of that research. Dr. Ryan Van Dre is an experimental psychologist at the Johns Hopkins Cannabis Science Laboratory. He's studied the health effects of cannabis for 26 years, and Dr. Natasha Wade, a neuropsychologist who studies the effects of substance abuse on adolescent brains. She recently analyzed data from 11,000 teens about how cannabis is affecting their development. welcome to you both to Science Friday. Thanks for having us, Flora. Thanks for having us.

Thank you both for being here. Ryan, you've said that the cannabis market has been allowed to run ramp it. Tell me more about that and answer what it means for you studying it. Yeah, so, you know, when I started, we were just looking about cannabis as a drug of abuse and people were smoking flour and that was it, right? And so the kinds of questions that we're concerned with now have changed dramatic. because now we have medical markets, we have adult use markets, and we have hundreds of different products. And so we have to understand what kinds of products are potentially

helpful or harmful for the medical application for dozens of different health conditions. We need to understand how the route of administration, the formulation, and the dose affect different people, and we have to kind of go back to our, is it a drug of abuse kind of questions, and revisit that in this novel marketplace. So we're trying to look at this from a lot of different perspectives. And, you know, there's been very few guardrails put up with regards to what kinds of cannabis products the industry can put out and the claims they can make about it. So as scientists, we're kind of constantly playing catch up to this to try to understand,

okay, well, there's this new kind of product. What does that mean? How does it compare to the more traditional forms of cannabis that we tend to come across? Yeah, that's interesting. I mean, it sounds like it's different than alcohol, right? Because there are actually different compounds. So it sounds like a lot more variables than other drugs. It's different compounds and it's different ways in which it's being used and purposes for which it's being used, right? And so alcohol is a fairly standard beverage. You drink it. And there's, you know, a couple different variants there. You've got kind of beer and wine and then you have spirits with canned. You've got oral dosing. You've got inhaled dosing with different kinds of devices. You have topicals.

You have suppositories. And so many different, each one of those variants changes the experience of the user. And then you throw on top of that a whole range of chemical entities. You know, alcohol is a single molecule in cannabis. You've got THC and CBD and CBN and CBG and a whole alphabet soup of different kinds. the chemicals that make up these products. Tasha, you study teens. Are teens using cannabis differently than they used to? Absolutely. I think that with all these different products, like Ryan was just saying, there's a lot more accessible to them. We're seeing that there's a lot

more co-use of cannabis, especially with nicotine products, which also might even change the experience and the downstream effects of use. And perhaps we'll make it worse, perhaps might mitigate some of the effects. But the jury still out, we still have a lot more to do to actually figure it out because everything is changing so rapidly right now. Well, tell me about this recent study where you looked at neurological development in teens who use cannabis. What did you find top level? Yeah. So we've been following some about 11,000 kids across the country for almost a decade now. And we have about seven years of data that we used here. We started when they're nine or 10 years old before they started using. And by the time they're 16 or 17 years old,

over 2,000 of those kids, we've identified as using cannabis now and have started using cannabis. And the big take home is that the kids who started using cannabis, the teenagers, were not showing the same gains and thinking abilities as their peers who were not using. And this was even after we control for whether they're using alcohol or nicotine or any other substances, prenatal exposure, early childhood, mental health concerns, family factors, socio-demographic factors. And so we see that there's some link between cannabis and perhaps reducing cognitive trajectories over time, not necessarily directly. We can't say it's causal, but there is a relationship between cognition and teens. And what do you mean exactly by

cognitive gains? Yeah, so we give the same test over. and over again every couple of years. And naturally, when they're teenagers, we expect them to improve, to grow, to learn. And so we expect them to do better when we're giving them the same test. And almost across the board, everybody is showing improvement. But those who are using cannabis are not showing the same level of improvement. And in some cases, it is actually kind of plateaued and don't show improvement at all. What about on the medical side? Are there health conditions that cannabis is showing promise for? Yeah, so there's a long history of cannabis being used and prescribed as a therapeutic.

And we're uncovering even more. So the endocannabinoid system, which cannabis modulates directly, is kind of a homeostatic kind of controller for a lot of different physiological systems in our bodies. And, you know, we've seen a tremendous promise for treatment of pain conditions. It's used to help treat the adverse effects. of chemotherapy if you're going through cancer treatment, as well as CBD, reducing seizures in rare forms of epilepsy. Aside from that, there's a lot of promising data emerging that shows that cannabis or other cannabinoids might be helpful for a variety of health conditions, a lot of which really have a huge unmet clinical need. PTSD is one. Another is autism, Parkinson's disease,

agitation and people with dementia. But again, you know, the science to kind of find the right product and to determine which patients it's most likely to be effective for is still evolving as we speak. I wanted to ask you about dose. Doe. Do we have a sense of how much THC, you know, you need for a sort of medical benefit for some of these conditions? There's a company based in Israel that's been developing a meter dose inhaler to help treat patients with chronic low back pain. And they have found efficacy for doses as low as a half a milligram of THC. So that's a dose that is imperceptible to the patient in terms of cognitive impairment or intoxication, anything like that. But it's effective on the clinical outcome. So the dose of THC needed to induce an

effect is going to vary based on what that effect is that you're looking for. And also, it's going to depend on the age of the person, sometimes the sex of the person, and also the experience that person has with using THC or other forms of cannabis. So it sounds like you might be able to get a health benefit without the high in some cases. Correct. And honestly, you know, that's where I see the future of cannabinoid medicine going. You know, cannabis is a very blunt tool in that it's very chemically complex. It has a number of different chemicals in it that hit a number of different receptors in our brains. It's a sledgehammer approach to medicine. Ideally, what we want to do is we want to utilize what we can learn about the cannabis plant

as a whole, identify the chemical constituents that drive very specific effects, and then develop novel therapeutics that really narrow down and can achieve target therapeutic effects. without side effects and adverse consequences. Hmm. We got to go to break, but when we come back, I want to ask you if recent policy changes are making cannabis easier to study or not. Does that sound okay? Great.

Of course. Stay with us. President Trump is trying to reschedule some medical cannabis products from Schedule 1, which includes heroin to Schedule 3, which includes, you know, ketamine and steroids. If it goes through, what would that rescheduling actually mean for your work? Would it make it easier to research cannabis? On my side, I do two kind of main lines of research. One is human laboratory studies where people come in and we give them the drug in the laboratory.

And the value in that is we can understand differences in the different kinds of products. And we can also understand how receiving that drug can impact performance, drug testing outcomes, and a variety of other things. So legalization would help us in terms of being able to purchase products that people can buy in dispensaries and bring those into our laboratory and study them. But perhaps probably the biggest impact on my side is that the other line of research that we engage in quite a bit is trying to understand, again, the health effects of medicinal cannabis use.

And right now, with it being federally illegal, a lot of patients, don't have access to regulated products. A lot of patients don't tell their doctors about what they're using, and the doctors can't prescribe them any cannabis product. And so the exact product that people are using is relatively unknown. It's not usually captured in their electronic health records. And so when we're trying to follow cohorts of people or trying to look at a health systems level,

you know, if people at Johns Hopkins Hospital have epilepsy or autism or Parkinson's or insomnia. You know, we have very little understanding of how many people are using cannabis, what kinds of cannabis products they're using, and what dose are for how long. And that's really limiting what we can say about the overall health effects of medical cannabis use for those health conditions. You know, as you both have noted,

cannabis falls into the sort of muddy territory of, due to medical and recreational. How are dispensaries navigating that? I mean, there's a coffee shop down the road from my house that has a list of CBD benefits, and you can get a bump of CBD for 250 added to any coffee product. And some of them might be conditions that have already been named, and some of them are definitely things that are not. And so I think it's not a dispensary. But going into dispensary. It's just out there, and it's a very large sign.

And it's, so I think, at least in California, there's a lot of information that's being put out there. You go and talk to bud tenders, and I have seen online you can do different trainings as a bud tender so that you can better advise your consumers who come in to buy certain products. So I think likely you're going to get very different experiences, depending on what shop you go into. But they, I think, are feeling confident in some way of providing some advice based on wherever they're finding their information from. And that's going to depend a little bit on which state you live in. So, for example, some states require that a pharmacist be available for consultation, who's had some kind of training, versus the bud tender who's really just a retail employee

and no different than the person who's checking you out at the grocery store and asking them for nutrition advice, right? They'll tell you something, but whether it's evidence backed or not remains to be seen. I mean, what advice would you give people who are, who, are shopping for these products? That's a loaded question that's way too broad to answer. So, you know, again, it's my whole thing is, is the dispensary model removes the healthcare provider from the conversation with the patients, especially in states that have legalized adult use because the adult use market has rolled the medical market in there. There's usually

no provider on site there to provide guidance, and we still don't have the quality. of data that we would want to have, even if we could make good recommendations. So I tell people all the time, you know, even if we had a large phase three clinical trial of some cannabis for a given health condition, the effect in that trial for that product wouldn't necessarily generalize to all the other products out there. And so, you know, the advice right now is for people to educate themselves on what different types of cannabis products there are, how route of administration impacts it. And, you know, unfortunately, we're still in an age where start low and go slow is the best advice you can give to anybody. But in addition to that on the

therapeutic side, it's you don't have to necessarily feel high to get a therapeutic effect. And so you want to gather as much information as you can from the Internet, talk to your doctor because your doctor should know if you're taking any kind of cannabis-related drug, especially for health purposes. And then it's a lot of trial and error from there. Tosh, I know you talk to teens and you go to high schools. What do you tell them? I mean, I try to be as honest with them as possible.

They are going to be making their own decisions in life very soon. It may not be legal for them to buy, but there's ways they find, right? And so I try to lay out for them, like, where's the riskiest? What is perhaps less risky, like some of the things Ryan just said? And then ultimately, especially while their brain is still developing, the message is wait, wait as long as you can. Because it's still going to be there. It's not, cannabis is not about to disappear. But if they have big life things going on right now and they just want to feel high, like there's go on a run, there's good runners highs, there's other things you can do.

But if, if they have big goals right now in their lives, I have not seen evidence in teens, in generally healthy teens, that it's going to benefit them in clear ways. And I do see that there's some evidence that it could harm them. and so they might as well wait in this very vulnerable life stage. Okay, last question. Is it frustrating to work in a field where there are so many unknowns and it's changing so rapidly? Or is it fun? What's it like for you to? I mean, it's why I'm in it.

I started in alcohol, and like you talked about, I think there's a lot of great research in alcohol, but it is, to some extent, simpler because it's alcohol and we can translate it in so many different ways. days, cannabis, we have to be on your toes constantly. And even, again, going into high schools, and they push back on everything. And they ask a lot of really great questions, right? And they're trying to figure out, well, if I just use once, just one time at a party or something like that. Like, they're really asking hard questions and trying to think it through for themselves. And at least when talking about alcohol, because I give similar talks in alcohol, you don't get the same kind of back and forth. And so to me, it makes it a lot more fun. There's a lot of potential good.

there's a lot of potential harm here. And so it keeps me very interested in it. Yeah, I'm right there with you, Tasha. It's fascinating. I think we've got 10 lifetimes worth of work that all need to be done next week. And the other part of this is that not only does cannabis research keep giving us new things to study and new directions to go,

but really everything we're doing right now has direct policy implications. which is rare in science that you can honestly say the work we're doing should and could inform the next policy decisions at the federal, state, or local level. And I really enjoy the fact that hopefully this impacts the betterment of public health because, as Tasha mentioned, cannabis has tremendous potential as a therapeutic and could help a lot of people, but it also has that dark side where it can cause a lot of harm. And I think if we use research and science to maximize the benefit while minimizing the harms, we'll all be better off.

Agreed. Well said. Dr. Ryan Vandre is a professor of psychiatry at Johns Hopkins, and Dr. Natasha Wade is an associate professor of psychiatry at UCSD. Thank you both for taking the time to talk to us today. Thanks, Flora. Thank you very much. This episode was produced by D. Peter Schmidt. If you have a question for us, we always want to hear it. Give us a call.

8774 SciFri is our number. That's 8774 SciFri. Thank you for listening. I'm Flora Lichten.