Marijuana and Medicine: Assessing the Science Base

Opening Statements 
by Principal Investigators

John A. Benson Jr.
Dean and Professor of Medicine Emeritus, Oregon Health Sciences University School of Medicine, Portland

and

Stanley J. Watson Jr.
Co-director and Research Scientist, Mental Health Research Institute, University of Michigan, Ann Arbor

John Benson:

Good morning and welcome. There has been unprecedented interest in recent years about whether marijuana or its constituent compounds should be used as medicine. Since 1996, voters in seven states have approved the medical use of marijuana. These state ballot initiatives, and the wider discussions they have spawned about appropriate national policies regulating marijuana, have been sharply divisive. Some have dismissed medical marijuana as a hoax that exploits our natural compassion for the sick; others claim it is a uniquely soothing medicine that has been withheld from patients through regulations based on false claims. Both sides cite scientific evidence to support their views.

To help illuminate this debate, the White House Office of National Drug Control Policy asked the Institute of Medicine to review the latest scientific evidence about the potential benefits and risks associated with use of marijuana. Stanley Watson and I led that review, which culminates with the release of the IOM report today.
It is truly an exciting time to conduct this study. With the assistance of more than 35 leading scientists in the field, we uncovered an explosion of new scientific knowledge about how the active components in marijuana affect the body and how they might be used in a medical context. The findings we are presenting today reflect the promise of this new research, as well as the invaluable input we gained in three public workshops. These events brought together scientists with dozens of people who use marijuana as medicine, as well as opponents of its use. There is remarkable consensus about the science -- science that suggests the potential of cannabinoid drugs for medical use. There is far less convincing data about actual medical benefits.

I will begin today by briefly outlining our conclusions about the clinical use of marijuana and its constituent components, known as cannabinoids. Dr. Watson will discuss what the future may hold in developing new drugs or new ways of delivering cannabinoids to patients.

In this study, we learned of more than 30 symptoms for which patients presently use marijuana. Most of these uses are poorly studied, and for that reason are not the focus of this report. For the most common medical uses, however, we found sufficient evidence to make a determination of marijuana's potential value as well as its potentially harmful effects. Our conclusions are backed by the rigors of evidence-based medicine, such as from confirmed controlled clinical trials.

Marijuana is a powerful drug that produces a variety of biological effects. While the most common effect is euphoria, marijuana also can lower a user's control over movement and cause occasional disorientation and sometimes unpleasant feelings. Some chronic users can develop dependence on marijuana, though withdrawal symptoms are relatively mild and short-lived. Except for the harmful effects from smoking, the range of problems associated with marijuana is not out of line with those of substances used in approved medicines.

From a medical standpoint, marijuana's effects are limited to symptom relief, not cures of disease, and are generally modest. For most symptoms, there are more effective drugs already on the market. However, physicians frequently encounter patients who do not respond well to standard medications, or for whom adjunct therapies are needed. For these patients, we found that cannabinoids appear to hold potential for treating pain, chemotherapy-induced nausea and vomiting, and the poor appetite and wasting caused by AIDS or advanced cancer. 

For other conditions, the data are not encouraging. We did not find compelling evidence that marijuana should be used to treat glaucoma. And with the exception of painful muscle spasticity associated with multiple sclerosis, there is little evidence of the drug's potential for treating migraines or movement disorders like Parkinson's disease or Huntington's disease. That is not to say that there are data that conclusively show that marijuana does not work, but rather that the data are either only weakly supportive, or most often, that the appropriate studies have not been done. So we call for clinical trials of cannabinoids for symptom management, in parallel with the development of safe delivery systems. 

Marijuana's potential as medicine is seriously undermined by the fact that people smoke it, thereby increasing their chance of cancer, lung damage, and problems with pregnancies, including low birth weight. For that reason, we do not recommend smoking marijuana for long-term medical use. While we see a future in the development of chemically defined cannabinoid drugs, we see little future in smoked marijuana as a medicine. That said, we concluded that there are some limited circumstances in which we recommend smoking marijuana for medical uses.

Marijuana should only be smoked in circumstances where the long-term risks are not of great concern -- such as for terminally ill patients or those with debilitating symptoms that do not respond to approved medications. Even in these cases, smoking should be limited to carefully controlled situations. Patients who are prescribed marijuana should be enrolled in short-term clinical trials that are approved by an oversight strategy such as institutional review boards, and involve only those patients most likely to benefit. Patients should be fully informed that they are experimental subjects and are using a harmful drug delivery system, and their condition should be closely monitored and documented under medical supervision. 

It is important to stress that the goal of these trials should not be to develop marijuana as a licensed drug. Rather, these trials should be done in parallel with the development of new, safe delivery systems of drugs related to the compounds found in marijuana.

Stanley Watson:

Although the issue of whether or not to permit patients to smoke marijuana is an important one, we believe it is really only a short-term consideration. Marijuana's future as medicine does not involve smoking. It involves exploiting the potential in cannabinoids such as THC, the key psychoactive ingredient of marijuana.

Presently there is only one cannabinoid-based drug on the market. Marinol, a THC capsule, is approved by the Food and Drug Administration for nausea and vomiting associated with chemotherapy, as well as for poor appetite and weight loss associated with AIDS. We believe that cannabinoids are an underutilized source of new drugs. Knowledge of cannabinoid biology points to several new, potentially promising avenues for drug development. Basic research has revealed a variety of cellular and brain pathways through which therapeutic drugs could act on the cannabinoid receptor systems.

But, besides the obvious difference that the THC capsule delivers a pure and chemically defined drug, whereas smoking delivers a variable combination of THC and related drugs, there is another critical difference between smoking THC and taking it in pill form. Smoking or inhalation delivers a rapid drug effect, whereas the THC capsule takes effect slowly, and its results are variable. There are many symptoms for which a quick-acting drug is ideal, such as pain, nausea, and vomiting. For that reason, we recommend development of a rapid-onset but non-smoked delivery system, such as an inhaler. Something like an inhaler would deliver precise doses without the health problems associated with smoking. We believe that clinical trials of cannabinoid drugs, therefore, should be conducted with the goal of developing an inhaler.

A second key issue to address in clinical trials is the extent to which cannabinoids' psychological effects, such as anxiety reduction and sedation, can influence the medical benefits they may bestow.

For new drug development, cannabinoid compounds and delivery systems that are produced in the laboratory are preferable to plant products because they deliver a consistent dose and are made under controlled conditions. Research should continue to investigate the physiological effects of both synthetic and plant-derived compounds, and the natural cannabinoids in the body. We recognize, however, that new drugs will only be developed from marijuana's compounds if public investments are made in research, or if the private sector has enough incentives to develop and market such drugs.

In addition to the medical questions, we were asked to assess whether marijuana acts as a "gateway" drug that causes people to progress to harder substances, and whether approving its medical use would increase its use among the general population. Although marijuana use often precedes the use of harder drugs in substance abusers, we found no conclusive evidence that something in marijuana causes this progression. Also, there is no evidence that marijuana use would increase among the general population if it were approved for medical use -- particularly if it were regulated as closely as other medications. Though related to the larger policy questions surrounding marijuana abuse, these issues are not directly relevant to the debate over medical uses, in our opinion. Thus we prefer to separate the medical use of cannabinoids from substance abuse. 

We are now happy to answer questions from members of the credentialed news media. Prior to asking a question, please state your name and affiliation.