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アンドルー・ワイル博士はアリゾナ大学医学部の Arizona Center for Integrative Medicine (アリゾナ統合医療センター)の創設者でありディレクター。博士の初期の著作(『ナチュラル・マインド』『チョコレートからヘロインまで』)は変容意識についてのもの。その他、『癒やす心、治る力』(1995)、『医食同源』(2000)、『ヘルシー・エイジング』(2007) などのベストセラーを出版している。


NM: As someone who has been researching cannabis for decades, how do you feel about the current legalization situation worldwide and in Japan, in particular?

Dr. Andrew Weil: I think the trend very clearly is that in most developed countries, cannabis is being made legal first for medical uses and then also for recreational uses. And that’s true throughout North America, in many European countries, and I think in some South American countries, as well. So, my feeling is that Japan is very out of step with other developed countries.

However, it has taken a long time to get where we are today in the United States. And cannabis is still in Schedule One of the Controlled Substances Act, making it unavailable at the federal level for therapeutic use. It’s urgent that we get it out of Schedule One. I think that’s going to happen very soon. Most U.S. states have legalized cannabis for medical use and 24 states have legalized recreational use.

NM: Please tell us about the history of cannabis use in folk medicine.

Dr. Weil: Cannabis has a long history of use in folk medicine throughout the world. In North America when it was used widely as a medicine in the 1800s and early 1900s, people were unaware of its use as an intoxicant. They didn’t know you could get high on cannabis. It was mostly available as a tincture for medical use, and if people had alterations of consciousness they didn’t mention it to their doctors. It was used for things like menstrual cramps and headaches and a wide variety of complaints. It was very safe. But it fell into disfavor in Western countries probably starting in the 1920s and 1930s when recreational use of cannabis began and the plant was demonized and then eventually made illegal.

NM: What characterizes cannabis as a medicinal plant?

Dr. Weil: I’m trained as a botanist as well as a medical doctor and the use of medicinal plants is one of my career interests. I teach at the University of Arizona about the medical botany and I have used a lot of medicinal plants in my practice of medicine. In general, I think that botanical medicine is safer than pharmaceutical medicine, that the chances of causing harm are much less.

Cannabis is a really special case. It has very complex, very unusual chemistry, unlike any other plant. Some of the compounds in it are not found elsewhere in nature. And there’s a wide array of chemical compounds that probably all contribute to its effects. I would say that cannabis is also distinguished by how safe it is. You can’t really calculate a lethal dose of cannabis. For almost all drugs that we use in medicine, the dangerous dose is not very much higher than the therapeutic dose. You really can’t kill people with cannabis. You can’t say that about most other medicines. So just on safety alone, it’s worth using it. And then cannabis has unique effects for a wide range of conditions, everything from the treatment of pain, treatment of asthma, treatment of immune conditions.

But I think there are also some problems with using cannabis as medicine. One is that because the chemistry of it is so complex, we don’t really know what constituents are the ones we really want, what’s responsible. And there are so many different forms of cannabis, there are many varieties, there are many strains with varying chemistry. I have many patients that want to use cannabis, and they who ask me what product should they get? I really don’t know what to tell them because there’s so many products out there. And I think for doctors, this creates difficulty because doctors like medicines that are standardized and that produce standard effects.

The other problem with cannabis is that there’s a wide range of individual responses to it. For example, some people can use cannabis before bedtime, and they say it helps them fall asleep. Others say if they use before bedtime, they can’t sleep, they stay awake all night. So that kind of variation in individual response also creates difficulties in the practical use of this. I think for doctors, we really need to have some sort of standardized products, not single compounds like Marinol, but a whole complex extract of cannabis that’s characterized, that we know what’s in it, like Sativex [a tincture with a 1:1 THC:CBD ratio] which is available in the UK and in Canada. I think we need products like that for doctors to feel more comfortable about recommending it.

NM: When you started cannabis research in the 1960’s, the endocannabinoid system was not yet known to exist. When it was discovered in the 1990s, what was your reaction?

Dr. Weil: We’ve seen this kind of pattern before with opioids where the compounds in opium were found to interact with opioid receptors in the body.  Why are these receptors there? They’re not there to interact with molecules from the poppy plant. They’re there to interact with compounds produced in our bodies that have the similar effects. The same thing with the endocannabinoids. I think for one thing this points out how connected we are to nature and that we’re not separate from plants and in some ways we’re meant to experiment with plants and see how they interact with us. It looks as if the endocannabinoid system regulates many very basic functions in the body. It regulates appetite, pleasure, pain, perception. Cannabinoid receptors are distributed throughout the body and brain, and I think that also accounts for some of the varied effects of cannabis and the possibility that it can treat many different conditions.

NM:  Does the fact that we have an endocannabinoid system set cannabis apart from the rest of the medicinal plants?

Dr. Weil: Yes, it does. Clearly there is a close relationship between our biochemistry and cannabis biochemistry. So, I think in some ways it’s logical that we find ways to use it.

NM: How do you define integrative medicine?

Dr. Weil: Integrative medicine is not alternative medicine. It doesn’t reject Western conventional medicine but tries to build on it. And the Center that I have at the University of Arizona trains physicians, and we try to teach them all the things they should have learned in medical school but didn’t. You know, starting with nutrition, with information about botanical medicine, with information about the strengths and weaknesses of other systems of medicine like traditional Chinese medicine, for example, about mind-body interactions, about spirituality and medicine, and a whole range of other subjects. So, as I said, we don’t reject conventional medicine and we don’t reject conventional medications, but we pay a great deal of attention to lifestyle and to the use of natural remedies whenever possible.

Integrative medicine is becoming very popular and mainstream in the United States, probably more so than anywhere else. I think one reason for that is our healthcare system is in such disarray and the cost is unsupportable. Integrative medicine offers the promise of lowering healthcare costs and improving outcomes both by shifting the emphasis to prevention and health promotion rather than disease management and then also by bringing into the mainstream treatments that are not dependent on expensive technology. I include pharmaceutical drugs in that category.

Our Center has graduated almost 3,000 physicians from an intensive two-year training and integrative medicine. The majority of medical schools in the US have joined a consortium for integrative medicine. There are many textbooks on integrative medicine out there. This is the kind of medicine people want. And I think the economic advantages of it are becoming more and more apparent. I’ve always said that one day we’ll be able to drop the word integrative and it’ll just be good medicine.

NM: Who studies at the Integrative Medicine Center at the University of Arizona?

Dr. Weil: Physicians who’ve completed residency training, and they’re of all ages. We’ve had people just out of residency, we’ve had people in their 60s who are very senior in their career. We’ve had people from all specialties, but mostly MDs, doctors of osteopathy and nurse practitioners and physicians assistants, some dentists. That’s our main training and it’s a two-year 1,000-hour fellowship, which is taught both in person and by distance learning.

NM: What are their motivations?

Dr. Weil: Good question. I think one major motivation is that a lot of these people have become very disillusioned with the practice of medicine as it now is. And many of them were thinking of dropping out of medicine altogether because the practice of it has become so unsatisfactory until they discovered this program and it renewed their reasons for why they went into medicine in the first place. I think also that some people come to us because they realize that there’s a big demand for this kind of medicine. Some people are sent to us by their institutions, by medical centers, who sponsor a person to do this because they see having someone on their staff trained in this way is an advantage that increases their competitive edge in the marketplace. So, I think there are a lot of different reasons why people come to us.

NM:  Do you teach nurses as well?

Dr. Weil: Yes, we train PhD nurses, but we have another program for other, what we call allied health professionals, which is everything from RNs, physical therapists, psychologists. So that’s a different training. And we also train residents. We have a program called Integrative Medicine and Residency that’s been adopted by, I think, over 100 residencies in North America, some in Europe as well. And that’s a condensed curriculum, I think, from about 150 hours. That’s a required, accredited part of residency training in a number of fields. And our goal is to have that be a part of all residency training so that one day, whether you go to a psychiatrist or a dermatologist, that person will have learned the basics of nutrition and health and mind-body interactions and botanical medicine and so forth.

NM: Is cannabis as medicine taught in the curriculum?

Dr. Weil: Yes, first of all, there’s been a big demand for information about cannabis from our Fellows, the people in our programs, they want to learn about it. So, we have developed a curriculum on the use of cannabis and this includes lectures on cannabis, particularly with the use of cannabis and cancer, but also generally in cannabis as medicine. That’s a course that we have available for people. And also, let me say, we’ve had quite a number of physicians from Japan who’ve come to us and have graduated from that program. I think we’ve got about 15 graduates in Japan.

NM: What is the major difference between conventional medicine and integrative medicine?

Dr. Weil: I think in conventional medicine in the U.S. — and this is probably true in Japan, as well — the time allowed for patient visits has gotten smaller and smaller. I remember at one point they talked about two-minute doctors in Japan. It’s not that much better in the U.S. With that little time, you can’t really take a full history. You can’t ask questions about a person’s lifestyle. I’ll just give you one example. There’s a condition that we call GERD, gastroesophageal reflux disease. I can’t tell you how many patients I’ve seen in the past, I’d say 10 years, who’ve gone to doctors and complained about indigestion or heartburn. And without any questions being asked about their diet, their use of coffee, their use of alcohol, whether they smoke, their stress, they’re put on a prescription for one of these acid-blocking drugs that are quite dangerous. You know, once you start them, it’s very hard to get off. They have many, many side effects that are not good. But nobody ever asked about what a person was doing that might contribute to their indigestion. And often these conditions can be cured just by making simple changes in what people are doing.

NM: Where do cannabis-derived pharmaceutical products stand in the larger framework of cannabis therapeutics?

Dr. Weil: I think most people would prefer to use cannabis in its natural state, whether they smoke it or take some oral preparation. They’re less interested in the pharmaceutical versions. And one of the best of those, the product Sativex that’s made in the UK, is not allowed in the U.S. Our FDA has banned its use and that’s really a shame because I think that’s one of the better products out there. Some years ago, our government allowed the use of Marinol, which is synthetic THC, especially for cancer patients. Most people did not like that. And people who were familiar with the effects of cannabis said that this was very different and they didn’t like the way it made them feel and they would prefer to use cannabis itself.

So as I said earlier, I think it would be useful to have pharmaceutical products available for doctors to recommend. But I think many people will still prefer to use whole cannabis in one form or another.

NM: Those who criticize integrative or alternative medicine cite a lack of scientific evidence as their reason. What is your thoughts on that?

Dr. Weil: Well, first of all, our curriculum in at our center is very evidence based and everything is supported by research. You know that when you hear conventional doctors say there’s no evidence, there’s no research. Often they’re just not aware of the research that’s there, they haven’t read the papers. So, it’s a matter of making them aware of it. There’s been a tremendous amount of research on cannabis. There’s still a lot more we need to know, but there’s a great deal of research and good scientific evidence supporting its use. We rate levels of evidence, and a high level may be a controlled randomized clinical trial (RCT), but there are also observational studies. There are case reports, and there’s a great deal of other kinds of evidence. And it’s worth keeping in mind that a lot of the medications that are on the market – this is certainly true in North America – have been backed by RCTs and are terrible drugs. They are very bad, and after some years people admit it and they get pulled off the market. That’s in conventional medicine. So, there’s evidence and there’s evidence; what I teach at our center is that we should use a sliding scale of evidence.

NM: Would you elaborate on scientific evidence?

Dr. Weil: The greater the potential of a treatment to cause harm, the stricter the standards of evidence it should be held to for efficacy. I think if we followed that rule in conventional medicine, we would have saved ourselves a lot of trouble. For example, in the late 20th century in this country, most women were urged to take hormone replacement at menopause. And we knew the risks of that, an increased cancer risk. We assumed there was evidence for the benefits that were being promoted and we didn’t have that, we didn’t follow that rule. I teach many patients breathing exercises, simple breath control methods that I find to be very effective. There have been very few RCTs on breath because it’s not taken seriously, but I’m not bothered by that because I know from my own experience that these things work, and the potential for harm is negligible.

NM: Do you think non-approved (non-pharmaceutical) medical cannabis should be available?

Dr. Weil: Yes, I’d like to see both routes that doctors could prescribe it and also that patients could go to dispensaries and buy cannabis preparations to use themselves, which is now true in most states. But that requires getting it out of this drug Schedule One. And as I said, I think that’s gonna happen fairly soon.

NM: If the prescription of non-approved medical cannabis products is allowed in the US, would there be many doctors who want to prescribe it?

Dr. Weil: I think so, just because the demand from patients is so great. And probably there are now many doctors who grew up during the ‘60s and experimented themselves with cannabis and know its effects and probably would be very interested in using it if it were legally available.

NM: Dr. David Meiri in Israel has stated that medical cannabis could be largely divided into two categories; pharmaceuticals containing specific compounds to treat specific diseases, and whole plant products for general wellness. Would you agree?

Dr. Weil: Yeah, I think I agree with that. I think that both should be available.

NM: What do you think is the ideal framework that would allow the maximum number of people to benefit from medical cannabis?

Dr. Weil: In most U.S. states there are dispensaries where most people have access to cannabis drugs. The problem is that, as I have said, they vary so much in quality and potency. But they’re there and people can have access to them. What we don’t have are preparations that doctors would feel comfortable prescribing. So, I’d like to see more development of that, but I think there will be both of those worlds.

NM: Do you think the reason some doctors do not want to prescribe non-approved medical cannabis is because they do not know enough about it?

Dr. Weil: Yes, I think there needs to be more information. That’s what we’re trying to do in our trainings by including this information for doctors who come to us and we have some online courses on cannabis medicine. Some of them are available to the general public. Yeah, I think education information is key. Cannabis is such an interesting plant. Cannabis sativa literally means “useful hemp.” It is one of the most useful plants ever. You know, it provides us with an edible seed, an edible oil, a high-quality fiber, a medicine, and an intoxicant. That’s a great many ways for one plant to serve us. It seems to me that cannabis just wants to serve us. It has as far back as you go in history. You can’t find truly wild hemp that has not been associated with human beings. It has co-evolved with us. And I think our society in recent years has been very unwise in rejecting it. Even in Japan, as in the US, this plant has been very important. There are so many fiber products that have been made from hemp, many textiles. The seeds are very nutritious. The oil from them is a very high-quality edible oil. You can make wonderful foods from them. And the medicinal uses are also part of that. So, I think we have not made good use of that plant and it’s time for that to change.

NM: I’d like to ask about THC. The euphoric effect THC has often been called an “adverse side effect.” But doesn’t THC also have significant medicinal properties? And how does this relate to CBD?

Dr. Weil: In the U.S., there’s been a great deal of promotion of CBD for a wide variety of conditions. Personally, I don’t think CBD does much by itself. I think it’s more useful when THC is also present. That doesn’t mean it has to be present in such amounts that it makes people crazy. But I think that the consciousness altering effect of THC is one important component of cannabis, although some people will not be comfortable with that. There are some forms of cannabis that are available here in dispensaries that are very mild in their psychoactive effect. And there’s some that are to me very, very strong, and I would warn people to be cautious about using. A lot of the pharmaceutical companies are trying to come up with compounds that have useful effects with no psychoactive effect. So, okay, if they want to do that, fine. But I think the psychoactivity is one important component of cannabis. And it may be that when people get high on it, the change in consciousness may be responsible for some of the benefit with, say, their perception of pain. That may be a useful effect.

NM: Of course, alcohol also produces euphoria.

Dr. Weil:  But alcohol is a much more toxic drug, a much more dangerous drug. And we’ve made that legal and make money from it. I think that, by comparison, cannabis is much safer, a much more benign agent.

NM: If cannabis is rescheduled to a Schedule Two category, would that mean that all products currently sold in dispensaries will be available for doctors to prescribe?

Dr. Weil: I don’t know. That would be up to the FDA what products it authorizes. And I think that doctors would like to see some sort of standardized products with known effects. That’s why I think something like Sativex would be much more acceptable than the array of things available in dispensaries. But again, one of the problems with cannabis compared to other natural products is the chemistry is so complex and so diverse. Which cannabinoids do you standardize for? And then it’s not just the cannabinoids, there are terpenes and essential oils and other things, all of which may contribute to the effects. How do you standardize for that? I don’t know the answer.

NM: As we speak, the 75-year-old Cannabis Control Act in Japan is about to be reformed.

Dr. Weil: I’m delighted to hear that there’s some movement in Japan, because as I said, I think Japan is really out of step with other developed nations now. It’s important to see attitudes there toward cannabis change. That’s great. I applaud your work in Japan and wish you all success.

三木直子は書籍翻訳家であり、また大麻に関する科学的エビデンスに基づいた最新情報を日本の医療従事者及び一般の人々に伝える非営利型一般社団法人 Green Zone Japan の共同創設者。Project CBD の日本語版のための翻訳も担当している。

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