5 Myths About Medical Marijuana

This article was originally published on July 21, 2015. At this point, marijuana is legal for medical use in nearly half of the country. But David Casarett, MD, author of the recently-released Stoned: A Doctor's Case For Medical Marijuana, wants to clear a few things up. Initially skeptical of marijuana's medicinal value, Dr. Casarett waded through the evidence, spoke to patients, and even tried the drug firsthand to figure out if the hype was warranted. A year and a half later, he's confident that marijuana has medical value, even though we have a lot left to learn about it. Below, Dr. Casarett busts a few of the biggest marijuana misconceptions out there. 1. MYTH: Medical marijuana always gets you high.
"There are two main ingredients in marijuana: One is tetrahydrocannabinol (THC); the other is cannabidiol (CBD). There are dozens of others, but those are the ones that we know the most about. They’re present in the largest amounts, and they’ve been studied the most. Of the two, it’s THC that has the most brain effects. It’s THC that gets you high. If you feel euphoric, or if you're unfortunate enough to have bad side effects (like hallucinations), those are due to THC. So, marijuana probably will get you high as long as it’s got some THC in it. "But, CBD, on the other hand, doesn’t have any of those brain effects. In fact, there have been studies using 300, 400, or 600 milligrams of CBD — which is a really whopping dose — with no psychological effects whatsoever. If it has effects, those are probably on the immune system and inflammation, although it may have some effects on neuropathic pain. "So if you’re using marijuana or marijuana products that are low in THC, then no, you won’t get high. That includes, most notably, the concentrated oils that are used [to treat] pediatric seizures." 2. MYTH: All strains are created equally.
"There are definitely wide differences in strains, most notably with respect to their concentrations of THC and CBD. There are so many differences, and they can be so hard to keep track of, that actually, many people advocate not paying attention so much to what the strain is, but instead asking the dispensary to make sure that whatever they sell is tested for THC and CBD concentrations.

"But, there’s another school of thought — which also has some credibility in my book — that says, 'Sure, THC and CBD are the main ingredients of marijuana, but they’re not the only ones.' And there are dozens of other cannabinoids present in smaller amounts that may be effective, too. So it’s certainly possible you could have two different strains with equivalent amounts of THC and CBD, but which may have different effects due to other cannabinoids that are in them. The problem is we just don’t know much about what those other cannabinoids do. So at least as a first pass, looking at THC and CBD concentrations is a good way to go. "[Researchers] are becoming interested in the possibility that a lot of the pain relief that you get from marijuana comes less from THC and more from CBD...However, most of the trials that I’ve seen for nausea use either THC or other synthetics that are not available for purchase through dispensaries. That doesn’t mean that CBD is not effective, but it does seem that the evidence is pointing in the direction of THC."

3. MYTH: Smoking marijuana causes severe lung damage.
"One risk that everybody I’ve spoken with thinks exists is the risk of lung damage. They say, 'Of course, if you smoke half a joint a day for years, you’re going to end up with lung damage and emphysema, like you do with smoking [cigarettes].' But, it turns out that’s not true. There have been a couple of very large, controlled studies that have failed to find any long-term pulmonary effects [in] people who are smoking [marijuana]. There might be a few changes in lung function, but there really isn’t any of the change that you see with chronic smoking. "There are two potential explanations for that. One is theoretical: We know that CBD is an anti-inflammatory. That’s important because the way that smoke particulates cause lung damage is by causing inflammation. So it may be that the CBD that’s in marijuana actually protects against some of that inflammation and damage.

"The other [explanation] is much more basic and probably the best one: It’s just a matter of dose. Most people who develop emphysema due to tobacco smoking do so after smoking one or two or three packs a day for decades. Think for a moment about what you’d be like if you smoked 40 or 60 joints a day for 20 or 30 years — lung damage would probably be the least of your problems. It could be that if someone were courageous enough to smoke that much marijuana...they would get lung damage. They probably wouldn’t care about that lung damage if they got it. But people generally don’t use that much."

4. MYTH: You can't get addicted to weed.
"On the flip side, a risk that many people don’t think about — that I certainly didn’t think about — that turns out to be very real is the risk of dependence and addiction. I honestly didn’t think that marijuana addiction was a real phenomenon, at least not in the same way that addiction to cocaine or heroin or even nicotine is, but it turns out it is. "The same circuits that create addictions to any of those other drugs are also involved in creating addiction to marijuana, with the same syndrome of craving and continued use in a way that’s disruptive to work, relationships, and physical health. There’s also a withdrawal syndrome...for people who use a lot regularly and then suddenly stop. People develop anxiety, agitation, and sometimes aggression in much the same way as somebody who uses alcohol continuously and then stops using. "It’s the same circuit that gets activated, and it works in the same way, but researchers also note that it’s not as likely to be activated. It’s very difficult to pin down the probability of addiction, because so many things determine it, but...somewhere around nine to 10% of regular users of marijuana will become dependent. That's compared to between 13 and 15% of [regular users] becoming dependent on other drugs, like cocaine. "One lesson seems to be that your likelihood of becoming addicted to marijuana is less than that of [becoming addicted to] other drugs. And, when people do become addicted to marijuana, it’s not necessarily as severe an addiction. Many people are addicted to marijuana using clinical psychiatric criteria, but still manage to function.

"However, all of the research that I’ve seen on marijuana addiction has been with recreational marijuana. So I don’t know how well that translates to medical [use]. Even if you say there’s a 9% chance that a 22-year-old who uses marijuana at parties is going to become addicted, does that mean that a 55-year-old administrative assistant...who uses it twice a week to get to sleep at night — is she really going to become addicted? Well, I wouldn’t dismiss the possibility, but there’s a big difference between those two people. I just don’t think we know enough about the risk of addiction in medical-marijuana users [to say they have the same risk]."

5. MYTH: Smoking pot causes mental illness.
"Part of the reefer madness message is that marijuana use causes mental illness in general and schizophrenia in particular. That’s not so much a myth, but the truth is more complicated than I thought. I think the jury is still out on this, but what I gleaned from a fairly contradictory set of evidence and studies is that it doesn’t seem that smoking marijuana causes schizophrenia. "On the other hand, there does seem to be an association between marijuana use and psychotic episodes, which consist of some of the symptoms of schizophrenia (including hallucinations and confusion). But unlike schizophrenia, psychotic episodes seem to be pretty acute, are often provoked by some external event, and resolve on their own. I think there’s pretty good data to indicate that marijuana use makes those episodes more likely. And people who are at risk of having them have them sooner if they’re marijuana users. That’s not definite, but that evidence seemed to me to be a little more persuasive. "In general, I think it’s pretty good advice that if you have risk factors for mental illness, you should be careful about using recreational drugs."