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Health Effects Of Marijuana


We'll learn about the latest scientific research on the health impacts of cannabis.

Special Feature The Marijuana State

KPBS investigates Prop. 19, a ballot initiative that would make recreational use of marijuana legal and allow cities and counties to tax and regulate the sale of the drug. "The Marijuana State" will air Tuesday, Oct. 19 at 9 p.m. on KPBS Television.

MAUREEN CAVANAUGH (Host): I'm Maureen Cavanaugh. You're listening to These Days on KPBS. There's been lots of talk lately about marijuana. A move to legalize the recreational use of marijuana is on the November ballot and it will be the topic of an in-depth KPBS/Envision report next month but while all this is going on, the use of marijuana as a medicine, largely as a pain reliever, even though legal in California, is still controversial. Many cities and counties are tightening restrictions on where and how medical marijuana can be dispensed. And critics are still challenging whether marijuana has any real efficacy as a medical treatment. Doctors at the Center for Medicinal Cannabis Research at UC San Diego have been working to find out just what value marijuana has in the reduction of pain and possible other benefits, as well as potential side effects. I’d like to introduce my guest. Dr. Igor Grant is director of the Center for Medicinal Cannabis Research at UCSD, and vice chair of the Department of Psychiatry. Dr. Grant, welcome to These Days.

DR. IGOR GRANT (Director, Center for Medicinal Cannabis Research, University of California San Diego): Thank you very much.

CAVANAUGH: And we’d like to invite our listeners to join the conversation. Would you like to see medical marijuana be treated more like other prescription medicine? Have you ever used marijuana to help treat a medical condition? Give us a call with your questions and your comments. Our number is 1-888-895-5727, that’s 1-888-895-KPBS. Dr. Grant, what is unique about the work that you’re doing at the Center for Medicinal Cannabis Research?

DR. GRANT: Well, as you may know, the center was established by legislation from the State of California and it was meant to determine if marijuana really has medical value. I think what’s unique is that there has not been any other sort of organized program of research into this area anywhere else in the country, you know, where patients have been enrolled in systematic clinical trials on cannabis.

CAVANAUGH: Yes, and so, as you say, tell us a little bit more about how the research – this study came to be. You have been tasked with this by the state, is that right?

DR. GRANT: Right. Well, after the voters passed Proposition 215 in the mid-nineties, which was the Compassionate Use Act, the University of California was approached by Senator John Vasconcellos, who was one of the leaders of that movement, to determine whether – how the state should respond, basically, and I think one of his ideas was that it would be very useful to get a good body of medical information to help guide state policy in this area, and so he authored a bill which the governor, Gray Davis, signed to set up a center at the University of California to attack this problem.

CAVANAUGH: Now before your center started research into medicinal marijuana, what kind of research had there been? What kind of research is your center building on?

DR. GRANT: Well, in the – Actually, going back to the sixties and seventies, there were periodic smaller-scale studies with marijuana which – some of which suggested that there might be benefits in certain kinds of pain, for instance, and some other conditions, nausea. But mostly that research ground to a halt by the time the eighties came along because marijuana had been rescheduled as a Schedule I drug, which means basically that the kinds of drugs that are in Schedule I are drugs that are harmful, addicting drugs, for instance, for which there is no known medical use. And I think placing marijuana there discouraged, I think, a fair amount of research. Plus, there are all the social and political ramifications, I think, so a lot of researchers just didn’t want to get into the middle of a marijuana debate.

CAVANAUGH: I’m speaking with Dr. Igor Grant. He’s director of the Center for Medicinal Cannabis Research at UCSD. And we are taking your calls about – 1-888-895-5727. Robert is on the line from Clairemont. Good morning, Robert, and welcome to These Days.

ROBERT (Caller, Clairemont): Thank you. I’m a delivery driver and I deliver to most of these dispensaries and when I’m in there, I would say 95, almost 99% of the people I see are young, healthy people and they’re just there to buy and smoke weed. I don’t see the medical aspect of it yet. And a lot of people I know who have a medical marijuana card are just potheads who didn’t have one before and are now using this as a loophole. So I don’t really see the medical benefit in it yet.

CAVANAUGH: Robert, thanks for the call. You know, Dr. Grant, a lot of people just simply don’t believe that really marijuana has any real value as a therapeutic drug. What have you found out about the therapeutic value of marijuana?

DR. GRANT: Well, we’ve completed several studies on a condition called neuropathic pain. Now neuropathic pain affects some people who have AIDS, diabetes and some other conditions, and it’s characterized by a burning, painful, very unpleasant hypersensitivity in the feet particularly, feet and legs, sometimes hands and arms. And it is a condition that’s difficult to treat. It doesn’t respond as well to traditional pain medicines such as ibuprofen, which is Advil, or even opioid medicines, morphine-type medicines. There are some treatments but not everybody responds to them and it’s the case that based on, certainly, animal research, there was evidence that cannabinoids might be helpful and so we’ve completed now several studies of people with AIDS neuropathy and some other conditions and it does appear that marijuana is helpful in reducing this kind of pain. Now, it is not magic. It just – I see it as another sort of drug in our armamentarium to treat difficult-to-control but disabling conditions. So I think it should be seen more in that light from a medical standpoint.

CAVANAUGH: Now you’ve been conducting a series of clinical trials at the Center for Medicinal Cannabis Research. Are there some that have yielded either inconclusive evidence or basically shown that marijuana does not have any effect?

DR. GRANT: Well, it’s rather interesting that the studies that we’ve done with this neuropathy condition that I’ve just mentioned, and we’ve completed one study also with spasticity in multiple sclerosis. Spasticity really means painful muscle contractions, stiffness, that some people with MS have that makes their life difficult. We found benefits from it in that condition as well. We have not done large scale studies—by that I mean, you know, thousands of patients.


DR. GRANT: And so it may be the case that that could come up with different results. But the series of studies we’ve done have found marijuana to be beneficial.

CAVANAUGH: We are taking your calls at 1-888-895-5727. My guest is Dr. Igor Grant. And Don is on the line from Carlsbad. Good morning, Don. Welcome to These Days.

DON (Caller, Carlsbad): Good morning and thank you for the opportunity to share a specific example. This goes to why I think medical marijuana is a good thing. This goes back before medical marijuana was legal in California. A friend of mine had cancer, was being treated with chemotherapy. He was prescribed Marinol to help control his nausea. Marinol, it’s my understanding, is synthetic THC. It was okay to buy it at what I thought was a very high price from the pharmaceutical company that sold synthetic THC but it was illegal to buy the herb. Now, so he went on the black market, bought marijuana illegally, smoked it, it controlled his nausea, where the Marinol when he took it, he would just vomit it back up again and of course the drill was, well, buy more Marinol, try it again.

CAVANAUGH: Right. Don, thank you for the call. And I’d like to get your reaction, Dr. Grant.

DR. GRANT: Well, I think the caller raises an interesting point which is that it’s correct that there is a legal preparation that contains essentially the active ingredient in marijuana in pill form. It’s called Marinol, as the caller said. And that is actually approved for use in nausea control and also in promoting weight gain in people who have severe debilitating weight loss. The problem seems to be for some patients is that the absorption of THC in oral form is very irregular for some people so, in other words, because of the chemical, this is an oily substance that is, you know, absorbed, as I say, irregularly, you don’t know when your peak blood level will occur and some people get very poor absorption, some people get good absorption, some people get delayed absorption, so it’s very difficult to do what we call titrating, that is giving yourself the adequate dose or the optimum dose to control the symptoms.


DR. GRANT: In other delivery forms like smoking or inhaling or perhaps there are now preparations that allow you to do a spray into the mouth so it’s absorbed through, you know, the oral mucosa. These may be more better ways of getting the THC into your body. So I’m not surprised by that anecdote. It would be great to have some studies that actually do head-to-head comparisons of Marinol and smoked or vaporized marijuana.

CAVANAUGH: How do the people in your research studies actually ingest the marijuana? Do they smoke it?

DR. GRANT: Yeah. The first studies actually involved smoked marijuana, and your listeners might be interested to know that the marijuana itself is actually provided by the federal government under a contract to the University of Mississippi. And so what the studies would be like is as follows. A person has pain, you know, we have a group of people with painful neuropathy. Some of them may be given placebo marijuana, which means that it is a marijuana cigarette from which the THC has been extracted, sort of akin to decaf coffee…


DR. GRANT: …if you want to think of it that way. And then others would be given marijuana cigarettes of different strengths. And so that’s how those studies are done.

CAVANAUGH: I’m speaking…

DR. GRANT: Now, currently…


DR. GRANT: …just to follow up on this, we’re also looking at vaporized marijuana, which means the plant material is heated, not so high that it burns but enough to get the vapors extracted and, hopefully, you know, that might get around, you know, the – all this downsides of inhaling a combusted plant material.

CAVANAUGH: And I want to talk a little bit more about that because I know that you have some real hopes for that vaporizing method of taking marijuana as – for its therapeutic value. I – We have to take a break. We will continue our conversation about medical marijuana with Dr. Igor Grant and take your calls at 1-888-895-5727. You’re listening to These Days on KPBS.

CAVANAUGH: I'm Maureen Cavanaugh. You're listening to These Days on KPBS. Doctors at the Center for Medicinal Cannabis Research at UC San Diego have been working to find out just what value marijuana has as a therapeutic drug. My guest is Dr. Igor Grant. He is director of the Center for Medicinal Cannabis Research at UCSD. And we’re taking your calls at 1-888-895-5727. Let’s go right to the phones and hear from April calling from Murietta. Good morning, April. Welcome to These Days.

APRIL (Caller, Murietta): Good morning. Thank you for taking my call. Good morning, Dr. Grant. I’m calling in this morning because I actually have a back injury that I’m waiting to have two different surgeries. And I took – I tried to take pain medication and all they do is make me ill. They don’t work. I have some pinched nerves. And they have me on Gabapentin, which I’ve been on a long time and I know that there’s some risk with that so I’m actually leaning towards that’s going to be the next thing I’m going to look into because I know that it will help, you know, it will help with the pain and it will help me sleep, I hope. So I wanted to hear what the doctor would say with somebody with a back injury like I have.

CAVANAUGH: Thank you, April. And Dr. Grant?

DR. GRANT: Right, well, I think if – Obviously I’m not going to prescribe over the phone…

CAVANAUGH: Certainly. Certainly not.

DR. GRANT: …without having evaluated April but depending on what kind of pain it is, if it has these components that I was describing before that are more like this neuropathic pain, you know, it’s certainly possible that cannabis can be helpful. Again, I think the evaluation of pain is a complicated thing. There are various kinds of medical treatments available, some of which work very, very well for people. Gabapentin is one of them but there are also drugs in the anti-depressant and anti-epileptic class, though they’re not used as anti-depressants or anti-epileptics in this case but they do have a beneficial effect on these kinds of pain. And, of course, there are surgical procedures, depending on what it is. So it’s part of a comprehensive package. Certainly, if these other methods are not working, I think, you know, consideration could be given to whether a physician would recommend the marijuana. The problem is, in the current state of politics and etcetera, there’s no legal source for the marijuana, and I think that’s one point I’d like to make to the listeners, is that by sort of mixing up the medical side with the politics and social policy, people are in a situation where a possibly effective agent is really not available. And this is where – We have to get past that somehow.

CAVANAUGH: And tell us what your opinion is of the current classification of marijuana as a Schedule I drug. Is that the real political problem that you’re talking about?

DR. GRANT: Well, it’s certainly one of them. And it is certainly based on the work we’ve done and I think based on the overwhelming evidence it’s not appropriate for cannabis to be sitting in Schedule I because it is, you know, almost certainly not useless. It certainly does have dangers, dangers of addiction. And so it should be a controlled substance, in my view, but there are many other controlled substances, morphine being one of them, that, you know, society manages very well. Now another argument that sometimes is made as well, you know, maybe the constituents of cannabis are helpful but marijuana as a, you know, total plan or such is not appropriate for medical use. And what I would say to that is that in the long term, I would agree that, you know, delivering a medicine by smoking has lots of problems attached to it, not the least of which you wouldn’t want a patient smoking in a hospital near oxygen tanks, you know, things like that. But we have to get from point A to point B. I think the first is to establish conditions under which marijuana or the cannabinoids are helpful and then move toward developing alternative products. But right now, we’re still kind of stuck at the first stage.

CAVANAUGH: We’re taking your calls at 1-888-895-5727. Steve is calling from San Diego. Good morning, Steve, and welcome to These Days.

STEVE (Caller, San Diego): Yeah, thank you. Yeah, I was wondering if there has ever been any research done on the side effects of marijuana as far as just a general condition of apathy, lack of drive, motivation, ambition, because that is something that I have seen, including myself when I used to smoke marijuana years ago, and I’ve seen it in so many other people.

CAVANAUGH: Thank you for that, Steve. Dr. Grant, any research about that, perhaps the mood implications or the marijuana’s effect on the brain?

DR. GRANT: Yeah. Well, certainly there are a number of effects of marijuana. It is a psychotropic drug, acts on the brain. It does produce, in many people, a state of sedation and it also can, in an active user, impair memory, coordination, it can change mood, so it’s not a, you know, like taking a baby aspirin or something like that. There are very significant effects. Having said that, many of the drugs we prescribe that are psychotropic for various illnesses, be it pain or psychiatric conditions, do have also significant side effects and – that have to be monitored. So, again, I think it’s a question of balance and appropriate use of something, warning patients about these side effects.

CAVANAUGH: Now some opponents of marijuana for personal or medical use say that the marijuana that you find on the street today is much stronger than it used to be, so strong it can lead to psychotic breaks. Do you – have you heard anything about that? Have you experienced anything like that in any of your trials? Your thoughts on that.

DR. GRANT: Yeah, well, there have been reports going back for 40 years or longer probably that some people can have adverse effects to marijuana that include psychotic breaks. Psychotic, by the way, means in my – when I use the term, a break with reality where a person can become highly suspicious or paranoid or can, you know, have hallucinations, these very severe kinds of effects. So these have been recognized for a long time and probably are, yes, dose related, that the stronger the marijuana, the more likely a person is to experience that. As to what’s on the street, you know, your guess is as good as mine. We have not tested what’s on the street. There are a lot of reports that the strengths are much higher than they used to be 15, 20 years ago. And maybe that’s true, I just don’t know.

CAVANAUGH: I’m speaking with Dr. Igor Grant and taking your calls at 1-888-895-5727. Stephen is on the line from Pacific Beach. And good morning, Stephen. Welcome to These Days.

STEPHEN (Caller, Pacific Beach): Hi. Good morning. Thanks for taking my call. Great show.

CAVANAUGH: Thank you.

STEPHEN: Well, I just had a brief comment. And that is, I think in America it’s about time that we stop weighing like your first caller, you know, truck drivers’ opinions and politicians’ opinions, and giving them equal weight to medical researchers and physicians which we’ve been doing. We make policy nationwide and many states make policy based on what politicians say even when there’s medical research and experts in the field who disagree with them. Often, those experts are disregarded and we do what the politicians say and it’s about time that the people, you know, stand up and say, you know, we need to listen to the experts here, which are oftentimes very different from what the politicians are telling us. And I think, just a final thing, is that these politicians oftentimes, and others, are opponents to marijuana use and stuff because there’s nothing in it for them. It’s an herb that can easily be grown in – by someone who even doesn’t have a green thumb in their backyard. So there isn’t a lot of money in it for the government. It’d be hard to be taxed if it was legal. There are difficulties. It can be controlled and, as your researcher on there said, that might be a good way but to have it completely illegal when many people need it, it’s just wrong and…

CAVANAUGH: Well, thank you for your comment. I appreciate that. Jennifer calling from San Diego. Good morning, Jennifer. Welcome to These Days.

JENNIFER (Caller, San Diego): Good morning, and thank you for taking my call. I definitely love your show. It’s part of my daily commute.

CAVANAUGH: Thank you.

JENNIFER: Well, I must agree with the previous caller, Stephen from PB, because I do agree that medical marijuana does help a lot of medically ill patients. I mean, I have a family member that dealt with cancer and marijuana was really the only thing that helped relieve a lot of the pain, you know, like what Dr. Igor Grant was mentioning about the nausea…


JENNIFER: …and all the other side effects that other prescription medication provided didn’t work. And I really think we need to have some sort of, you know, conformity in screening applicants, you know, that they are being used for medical purposes. And I do see how the public’s opinion about these dispensary are kind of tainted because, you know, the first caller being a delivery driver saying, yeah, there’s healthy people going in there and then it’s like a little – it just doesn’t make sense for someone who does need it and doesn’t have access to it and someone who obviously don’t need it is getting these medical cards and going in there and buying what they need conveniently.

CAVANAUGH: Well, Jennifer, thank you. Thank you for that comment. I appreciate it. Dr. Grant, I wonder, do you have an opinion about whether or not the recreational use of marijuana should be legalized?

DR. GRANT: No, I – Well, I have a personal opinion but I’d rather not express that on the air…


DR. GRANT: …because I’m here really representing, you know, the university. But I think that it’s important to basically separate the medical issues here from these other social policy issues. This has been a problem, I think. I think if the research confirms what we believe to be true, that the marijuana or the constituents of marijuana can be medically helpful in several diseases, then we have an obligation to make these things available to patients who need it. And the question then becomes how do we do that? I think the present system with dispensaries and people trying to get marijuana on the street wherever they can is not a good medical model. And I think, I hope, most of your listeners would agree to that. You know, you wouldn’t want to buy pills for any other condition on the street, not knowing what’s in them. So we need to get to a point where if cannabis is prescribed, in whatever form, that the patients can be assured of their purity and potency, just like we would expect with any medicine.

CAVANAUGH: Would you expect that it should be dispensed at a pharmacy just like any other drug?

DR. GRANT: I think that would be ideal, personally.

CAVANAUGH: What would you say, Dr. Grant, are some of the common misperceptions of the impact of marijuana on the human body?

DR. GRANT: Well, I think the main ones are that – Well, there are two degree – two directions of misconception. The one side is people who believe that this is a very harmful drug, it’s addicting, that it will damage your brain, it will damage your lungs, cause cancer, all sorts of things like this, that it’s a gateway drug and so forth. I think that these concerns are quite overstated, although in terms of, certainly, young people, you know, junior high school students or something getting into marijuana, that is not, certainly, anything anyone should support and we should discourage that. But on the other hand, there is very little evidence that use of marijuana, at least the way it’s used in this country, leads to brain damage, lung damage, or anything like that. On the other side, though, are people who say it’s a perfectly harmless drug, and that’s not true either. It does have dependence producing properties. People sometimes have real trouble stopping using marijuana. It can affect their day-to-day life. So that’s not good either. So I think we should have a proportionate and balanced view of the sort of risks and benefits here.

CAVANAUGH: And let’s go to the phones again. We’re taking your calls and we’re also encouraging you to go online and state your opinion there at Debi is calling us from Carmel Valley. Good morning, Debi, and welcome to These Days. Hi, Debi? Okay, Debi – Debi, are you on the line?

DEBI (Caller, Carmel Valley): Yes.


DEBI: Yes, I am.

CAVANAUGH: Yes, hi. You want to tell us your question?

DEBI: Well, I have a comment.


DEBI: I’m a 58-year-old conservative woman who’s had chronic sciatic pain. I was given opioids that I could not tolerate and then told I had to just bear it for all these years. And finally my son convinced me to try medical marijuana and I have to tell you that I had remarkable results with it. I haven’t tried it since because, you know, I haven’t been in town but I was just amazed by it. And I was taken also by the clinic, how clean. And my experience was there were people in there, there was a veteran and there was an older man who had had chronic pain such as mine, and I had a positive experience going in the dispensary that I visited.

CAVANAUGH: Thank you for that comment. I appreciate your call. Doctor, I said that we would go back to this vaporized form of marijuana that you’ve been working with. Have you been actually working with that in your clinical trials?

DR. GRANT: Yes, we’ve now had three projects on this vaporized marijuana. Again, to remind people, it’s basically putting the marijuana plant into a contraption that will heat it but not to the point of burning but enough to cause vapors to come out. And so initially one of our investigators, Dr. Donald Abrams at UC San Francisco, showed that this type of vaporized inhalation produced equivalent amounts of absorption of this THC as smoking did. So it seems, from that perspective, equivalent. And now we have two studies going on with pain, one is at UCSD, one is at UC Davis, that’s looking into really how well does it work with clinical patients. I don’t have the answers to that yet. Those studies are ongoing, should be finished next year sometime.

CAVANAUGH: And the advantages of that vaporized form of marijuana, you told us, one, that it wouldn’t necess – it would be hard to smoke marijuana next to an oxygen tank in a hospital. What are some others?

DR. GRANT: Well, smoking any plant material introduces – Well, first of all, it’s just, at the simplest level, irritating and some people find it, you know, just very unpleasant. People who don’t know how to smoke would need to be taught to smoke and, you know, they may not want to get into that. And, more, I guess, seriously that, you know, if use was for very long term, smoking has the theoretical possibility of injuring your lungs. I’ve said, however, that it’s very interesting and it was a surprise to me that the studies that do exist, that have looked at sort of long term users of marijuana and compared them to non-users have just not found much evidence that there is, say, more emphysema or lung cancer or anything like that that could not be explained by tobacco so…

CAVANAUGH: I see. Now as you continue your studies about the medicinal use of cannabis, are there any kind of discoveries that are coming out of this that perhaps have other implications? I read somewhere that there’s a possible use as a diet drug in some way. Tell us about that.

DR. GRANT: Right. I think one of the exciting things is that there is a lot of research now that is looking at how does our internal cannabinoid system work? Just to – in brief, in our bodies, our brains and our other organ systems, there are actually little networks of cells that communicate using what are called endocannabinoids now this is not – they are not – it’s not THC itself.


DR. GRANT: But these are molecules that mimic, if you will, the effects, some of the effects, at least, of THC. And we’re beginning learn more and more about what this system, this endocannabinoid system, does. One of the things it does is control movement. It has an effect on mood, the irritability of the brain and so forth but there are many other effects as well, and one of them you’ve mentioned. People who use marijuana say they have – they can get the munchies. Well, it turns out to be true that the endocannabinoid system has an effect on eating behavior. And so it stands to reason then if you develop drugs that block the system, they could be used in – as appetite suppressants, weight control drugs. And, in fact, there are drugs now based on the cannabinoid system that are being tried out as weight control pills. One of them, which is called rimonabant, actually was tried in Europe and it works but it had some side effects in terms of depressive symptoms so it’s not gone forward.

CAVANAUGH: I see. This is all fascinating. Dr. Grant, I’m so glad you could take the time out this morning and speak with us. Thank you so much.

DR. GRANT: You’re very welcome.

CAVANAUGH: Dr. Igor Grant is director of the Center for Medicinal Cannabis Research at UC San Diego. He is also vice chair of the Department of Psychiatry. If you’d like to comment on anything that you heard, please go online, And stay with us for hour two of These Days coming up in just a few minutes here on KPBS.

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