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Testimony on Substance Abuse by Alan I. Leshner, PH.D.
Director, National Institute on Drug Abuse
National Institutes of Health
U.S. Department of Health and Human Services

Before the Senate Labor and Human Resources Committee
July 28, 1998

Mr. Chairman and Members of the Committee, I am pleased to have the opportunity to discuss with you some of the advances science has made in our understanding of drug abuse and addiction and how we can continue to use science to approach this complex problem. Simply put, advances in science, particularly over the past decade, have virtually revolutionized our understanding of drug abuse and addiction. We have learned, for example, that although initial drug use is a voluntary, and therefore a preventable behavior, drug addiction is in fact an illness caused by the effects of prolonged drug use on the brain. Addiction is a chronic illness, similar to other chronic diseases, characterized for many people by occasional relapses to drug use, even after successful treatment experiences. And it is important to state at the outset that we have numerous effective, science-based and tested treatments in our clinical toolbox. Addiction is a treatable, though chronic and relapsing, disease.

The state of addiction -- defined as compulsive, often uncontrollable, drug seeking and use even in the face of negative consequences -- comes about because prolonged drug use has modified the brain's functioning in ways that last long after the individual stops using drugs. And I should point out that we know a great amount about how drugs modify brain function to produce addiction. In fact, I frequently say we know more about drugs and the brain than we do about any other aspect of brain function. For example, scientists have identified and cloned the receptors in the brain for every major drug of abuse. They have identified the cellular sites where drugs like cocaine, marijuana, and opiates bind to the brain. And in the last two years it has become clear that although each drug of abuse affects the brain in a particular, individual way, they all share some common brain pathways, which further suggests that there is a common brain essence to addiction.

We can actually see many of these brain changes with sophisticated modern neuroimaging tools. We can now look into the brain of a conscious person and see what is happening as he or she experiences a drug. This particular poster, [Poster 1] shows the effects of cocaine on the brain. Using functional magnetic resonance imaging (fMRI), we can also observe how the brain of a drug user responds as they experience the "rush," the "high," and finally the craving of a commonly abused drug like cocaine.

We can now also see the long lasting effects that drugs have on the brain, even after a person has stopped using the drug. This second poster shows a positron emission tomography or PET scan of a monkey brain [Poster 2] and it demonstrates that just 10 days of amphetamine use can produce very dramatic and long-lasting changes in brain functioning. The measure here is the ability to produce a brain chemical a neurotransmitter called dopamine which, among other things is necessary for the normal experience of pleasure. The red and white connotes more ability to produce dopamine, blue is less. The top row shows, in white and red, the ability to produce dopamine in a normal monkey before drug exposure. The second row shows us the brain of the monkey four weeks after being given amphetamine for 10 days. Note the dramatic decrease in the ability to produce this important brain chemical. At six months, dopamine production ability is still reduced, it returns by 80% after one year, and to full capacity by two years. The point here is that the brain changes produced by heavy drug use can last a very long time after the individual stops using drugs. Importantly the particular changes you see here, we believe, are involved in the tremendous cravings, depression and other disturbed behaviors observed in methamphetamine (a drug similar in structure to amphetamine) addicts even during long periods of abstinence.

Changes in dopamine function, by the way, are common to all addicting substances alcohol, nicotine, marijuana, heroin, cocaine, amphetamines and we believe that dopamine changes are involved in the common essence of addiction.

Research showing that the brain can change in both structure and function after repeated exposure to drugs and this is essentially why we call drug addiction a brain disease. It is as if a metaphorical switch in the brain is thrown following prolonged drug use and the individual moves from a state of voluntary drug user into the state of addiction, characterized by compulsive, often uncontrollable drug seeking and use.

The fact that addiction is a brain disease does not mean it just affects the brain. It is more complex than that. It also includes very important behavioral and social context elements. For example, we know that behavioral and contextual events like stress, or exposure to the individual's once familiar drug using environment can trigger tremendous cravings for the drug, thus creating the potential for relapse. This is why it is important that all aspects of the addict's life, including these behavioral and social context elements are addressed in the individual's treatment regimen, so they can begin to recognize these environments or factors and modify their behaviors. That is, successful treatment for addiction must include attention to the behavioral and social context aspects of the disorder, not just to its biological underpinnings in the brain.

This compulsion to use drugs is what really matters when we begin talking about treating the disease of addiction. Other aspects of addiction, such as physical withdrawal symptoms, can be relatively easy to overcome. But drug cravings and the other compulsive behaviors associated with addiction are extremely difficult to control and they are actually responsible for the impact that addiction has on the family, the workplace and the broader community.

This now brings me to the second point of my earlier statement-- addiction is a treatable disease. Because addiction is such a complex disease, including biological, behavioral and environmental components, it is not a simple disease to treat. Moreover, it is similar to other chronic illnesses, such as diabetes and chronic hypertension, which are often relapsing in nature and must be managed over time. All chronic illnesses, including addiction, require repeated or booster treatments over the course of the patient's life.

The good news is we already have many effective addiction treatments in our clinical toolbox and many others that are in various stages of development. Like all other medical illnesses, we have a variety of effective treatments for addiction but we desperately need to have more and even better ones. For example, we now have methadone and LAAM (levo-alpha-acetyl-methadol) for opiate or heroin addiction, and will be seeking approval, jointly with a pharmaceutical company, for a new class of anti-heroin medications over the next year. For tobacco addiction, there are several nicotine-replacement therapies, such as the patch and gum, and several non-nicotine ones as well, such as buproprion (Zyban ) that are readily available. We also have numerous behavioral therapies, like cognitive behavioral or contingency management therapies, that have been shown to be very effective in treating addictions.

Research has shown that although behavioral and pharmacological treatments can be extremely useful when employed alone, integrating both treatments, in ways specific to an individual's needs, is likely the best way to treat addictive disorders. We have also found that because addiction can affect every aspect of a person's life, a treatment program must address not only the individual's drug use, but must also help restore the individual's abilities to function successfully in society. It is critical to treat the whole person. And to reiterate the point, we have many treatments that yield success rates quite comparable to those for other illnesses.

Moreover, research has shown addiction treatment to be quite effective in reducing not only drug use but also in reducing the spread of infections like HIV/AIDS and in decreasing criminal behavior. Thus drug treatment affects not only the individual patient but also has benefits in terms of both public health and public safety.

As with all diseases, science has not only yielded great benefits to date, but also provides the best hope for the future. My institute is committed to continue supporting a broad array of research designed to improve existing treatments, while we simultaneously develop new and improved approaches to drug treatment. Moreover, given the recent dramatic advances we have made in both understanding of addiction and in its treatment possibilities, NIDA is committed to working intensively with the drug abuse professional community to actively transfer this knowledge in a proactive way into the community setting, thus greatly improving how we treat addiction in this country.

To accomplish this difficult task, the National Institute on Drug Abuse (NIDA) is planning to launch a National Drug Treatment Clinical Trials Network. The Network will provide the infrastructure to ensure that all potential addiction treatments are tested in real life settings. It will enable us to systematically, rapidly and efficiently test the effectiveness of behavioral, psychosocial and pharmacological treatments in large-scale, multi-site clinical trials. Moving treatments from the laboratory, to the clinic, to the community is the next rung of the ladder for national treatment improvement.

We have come a great distance in our approaches to understanding and treating drug addiction, but we still have quite a distance ahead of us. We can improve the quality and availability of treatment in this country if we put treating addiction on equal footing with other chronic diseases. The science in this field is strong and the success rates for treating addiction are comparable or better than those for many other illnesses.

Thank you once again for inviting me to participate on this panel. I will be happy to answer any questions you may have.

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