[Editor's note: This article is from 2007. Some newer treatments and current statistics are not included here. See further information on BrainWeb]
sections include:defining and discovering addiction, prevalence and contributing factors, drugs, addiction, and the brain, tolerance and withdrawal, treatment, prognosis
Of the thousands of drugs in nature and the many thousands that people have made in laboratories, only a relative handful are used regularly for their effects on our mood, thinking, or behavior. The most commonly used drugs in the world are caffeine (found in tea, coffee, and certain soft drinks), nicotine (in tobacco), and alcohol (in wine, beer, and a variety of distilled liquors). These drugs are legal in most countries, if not always freely available to everyone. Alcohol, the most frequently used brain depressant in most cultures, and a major cause of illness and death, is discussed in greater detail here.
Other categories of drugs, such as the opioids commonly used to treat pain, are either restricted to medical use or prohibited entirely. Attitudes toward prohibited drug use (nonmedical use) vary remarkably across cultures. Penalties for illegal possession can range from modest fines to imprisonment, and sometimes to death. In the United States we use the term drug abuse in two very distinct ways. In a legal and legislative context, it refers to using any drug illegally. Technically, the definition would include not just the use of an illicit drug such as marijuana, but also the consumption of alcohol by anyone under the legal age. In a medical context, however, the use of a drug is not by itself “drug abuse,” even if the drug is illegal. However, when drug use begins to cause problems for the user, it becomes a medical concern—even if the drug’s use is legal. Doctors can designate such behavior “abuse” of that particular drug and consider such use to be a medical or psychiatric disorder. Admittedly, these definitions of abuse can be confusing. Most other countries use a somewhat different system of categorizing disorders, called the International Classification of Disease. This system does not include a concept of drug abuse but uses instead the notion of harmful use, defined as a pattern of psychoactive substance use that causes damage to health. Social problems, such as arrests or marital problems resulting from the drug use, are not part of this definition.
We cannot describe the appearance or characteristics of drug abuse or dependence in a simple way, because the concepts cover a wide array of drugs with distinctly different effects on the brain and behavior. The drugs that people use for their effects are generally categorized into ten groups or families. The World Health Organization uses the following categories: alcohol; opioids (opium and its derivatives, including heroin and morphine); cannabinoids (such as marijuana); sedatives or hypnotics; cocaine; other stimulants, including caffeine; hallucinogens; tobacco (nicotine); volatile solvents (inhalants); and other drugs or use of several drugs together.
Choosing 10 categories is somewhat arbitrary, dictated in part by a coding system that permits only ten categories. Other, more flexible classification systems, such as those used by the American Psychiatric Association, define 12 or more categories, allowing separate categories for amphetamine stimulants, phencyclidine, and mixed substances.
We could create several more groups or families since both classification systems have a miscellaneous category that includes a grab bag of drugs with little in common. Some of these substances are rare in the industrialized world but quite commonly used in less developed areas. For example, betel nut, which contains the drug arecoline, is widely used in Asia and India and is thought to be the fourth most commonly used drug in the world (after caffeine, alcohol, and tobacco). Other agents in the miscellaneous category include anabolic steroids and such nitrite inhalants as amyl and butyl nitrite.
The only property common to all these agents is that they affect the brain and that some people choose to ingest, inhale, or inject them to experience their effects. Of course, we take an even wider array of drugs than are in these 10 to 12 categories, but those other drugs are customarily used to alter some function of the body—for example, to reduce a fever, cure an infection, control diarrhea, and so on. In some instances, drugs that affect the brain may be used for another purpose. Wine can be defined as a food or a sacrament; betel nut freshens the breath; opioids relieve pain as well as alter mood and produce euphoria.
Defining and Discovering Addiction
Despite great advances in knowledge over the past decade, experts do not agree completely on the nature of addiction. What is generally obvious is that drug use, whether the drug is alcohol, nicotine, heroin, or cocaine, begins as a voluntary behavior. The user may be entirely ignorant of the risks or entirely familiar with all of them, including the risk of getting “hooked,” or, to use the medical term, becoming dependent. The individual tries the drug nevertheless, either because of peer pressure or because he or she is seeking some expected change (euphoria, tranquility, relaxation) that appears to be worth the risk. Not everyone who tries a drug repeats the experience, even if the effects are satisfying. On the other hand, some who initially have an unpleasant reaction, such as nausea from opiates or from too much nicotine, will persist until they can tolerate these unwanted effects.
In time, some users begin to feel that they need the drug just to function normally; they no longer have the same freedom that they once had to choose whether or not to use it. The degree of severity of this loss of flexibility of choice varies from mild to severe. At its extreme it is sometimes described as a chronic, relapsing disorder characterized by compulsive drug seeking in which use of the drug takes priority over other things the user once valued, such as family, friends, reputation, and even health and life.
How the drug dependence affects a person’s life depends in part on the specific substance, the culture, the individual, and the circumstances influencing its availability. For example, dependence on smoked tobacco (cigarettes) may at first have very little impact on an individual’s functioning. As the financial cost of daily smoking escalates and employers place limits on smoking in the workplace, the dependence can become a burden. And after many years, daily use of cigarettes may lead to lung cancer, heart disease, or emphysema.
When an adult becomes dependent on illicit drugs, such as cocaine or methamphetamine, his or her family might first notice that money is in short supply. The person may show changes in mood and behavior. For instance, both methamphetamine and cocaine induce talkativeness, a sense of exaggerated optimism, and sometimes irritability. The user may need less sleep and less food. When the drug is unavailable, the opposite effects appear. The user may exhibit a depressed mood, sleepiness, and lethargy. As the syndrome progresses, some of the common toxic effects may become more apparent: repetitive behaviors, suspiciousness, and eventually a toxic psychotic state with auditory hallucinations and paranoid ideas.
Many families have difficulty recognizing substance use, abuse, or dependence in young people because the behaviors vary so much depending on the specific drug, and because in the early stages the symptoms are not very specific. With illicit drugs such as heroin or cocaine, the first clue that there is a problem may be an inordinate need for money or the appearance of new and unusual behaviors aimed at getting money. An unusual decline in school grades is typical, although this can be a sign of a variety of problems unrelated to drugs. Changes in mood or sleep patterns (insomnia or hypersomnia) are also common, although these too may be due to other psychiatric disorders, such as depression or anxiety. Young people are far more likely to use and to become dependent on alcohol and tobacco than the more illicit drugs (though purchasing all of these is illegal for teenagers). Parents often first detect a child’s regular use of marijuana from a change in attitude toward school or sometimes by the peculiar sweet smell of marijuna smoke. They can also often detect if their children use alcohol during the day or if alcohol is disappearing from the house. Determining from observation alone whether people have become dependent on drugs is more difficult.
There is no medical test to determine whether a person is substance-dependent, but toxicology screens (drug testing) done on blood and urine specimens can reveal the presence of many chemicals and drugs in the body. The accuracy of such tests depends on the substance itself, when it was taken, and the testing method used.
Prevalence and Contributing Factors
When we view the full spectrum of psychoactive drugs, legal and illegal, the probability that an individual will develop a drug-abuse or drug-dependence problem at some point in his or her life is surprisingly high. In the United States, a survey in the early 1990s found that when prescription drugs are included, about 26 percent of people 18 or older at some time meet the criteria for either substance abuse or dependence. For illegal drugs and nonprescribed use of prescription drugs, the lifetime rate was about 8 percent.
Many factors contribute to the likelihood of developing dependence on a drug. Perhaps the most important is use, which depends on access. For example, the likelihood of becoming dependent on heroin for the population as a whole is less than 1 percent, but it is 23 percent for those who have used it. For the population as a whole, the lifetime rate of cocaine dependence is less than 2 percent, but it is 17 percent for those who have used it. Not everyone is equally exposed to illicit drugs; those who live in neighborhoods where they are available are more at risk for trying them. For legally available drugs, the lifetime dependence rates are high. Among people who use alcohol at all, the dependence rates are about 21 percent for men and 9 percent for women. Problems of drug dependence are also higher among doctors, nurses, and pharmacists, who have greater access to a wide range of drugs than other groups with comparable socioeconomic status.
Some people who try drugs seem to be more vulnerable than others to becoming drug-dependent. It is now clear that genetic (hereditary) factors play an important role in an individual’s vulnerability to virtually all forms of drug dependence. Also increasing the risk of dependence is the presence of certain other psychiatric disorders. For example, the risk of drug or alcohol dependence is substantially higher among young people with conduct disorder and older people with antisocial personality disorder. The risk of alcohol dependence is sharply higher among those with bipolar (manic-depressive) disorder. In the National Comorbidity Survey, 51 percent of people who were diagnosed with some form of addictive disorder in their lifetimes had at least one additional psychiatric diagnosis.
Drugs, Addiction, and the Brain
Over the past 30 years, science has made great progress in understanding how the drugs involved in addictive disorders work and how they affect the brain. Each of the major categories of drugs affects the brain by acting on a distinct set of receptors located on neurons, alcohol being the possible exception. For example, the opioids act at natural opioid receptors located on neurons in the brain and the gut, and on white blood cells. Similarly, the anxiolytics (anxiety-relieving drugs), such as the benzodiazepines, the cannabinoids (any of various chemical components of marijuana), and phencyclidine, act at their own special receptors on neurons in the brain.
Cocaine acts on specific sites on nerve membranes that are very close to the sites responsible for sopping up newly released neurotransmitters and transporting them back into the neuron for recycling. When cocaine binds at this site, the transporter system doesn’t work and neurotransmitters such as dopamine, serotonin, and norepinephrine increase in the space between neurons, allowing these transmitters to produce an exaggerated effect.
These neural receptors obviously did not develop just so we could experience the effect of these drugs. They are the sites where our nervous system’s signaling chemicals (the neurotransmitters) exert their actions. However, when these receptors are flooded regularly with ingested, injected, or inhaled chemicals that are in higher concentration or that last longer than the body’s own neurotransmitters, the brain undergoes changes.
Some of these changes probably contribute to the behavioral syndrome that we refer to as “addiction” or “drug dependence.” Some drugs may also lead to either temporary disturbances or long-lasting damage to the brain. These disturbances may lead to a number of abnormal mental disorders other than addiction: psychosis, mood disorders, sleep disorders, and so forth.
Tolerance and Withdrawal
Recent research has led to a greater understanding of tolerance and physical dependence, the conditions responsible for withdrawal syndromes when people stop taking certain families of drugs after a period of use. Tolerance and physical dependence (physiological dependence) were once considered the essence of drug addiction. Doctors thought that all truly addicting drugs produced obvious withdrawal symptoms. Indeed, when people stop using alcohol or opioids such as heroin, even untrained observers have no trouble seeing the withdrawal symptoms. Opioid withdrawal begins with anxiety, runny nose, yawning, headache, and nausea. If an individual is severely dependent, he or she will also suffer cramps, diarrhea, vomiting, gooseflesh, fever, and kicking movements of the legs (hence the slang “kicking the habit”). These acute symptoms, even when severe, are largely over within a week or two, but it takes much longer—perhaps months—for the person’s brain to return to normal functioning. We now believe that subtle, persistent changes in brain function (particularly in those systems that regulate our capacity to experience pleasure from normal activities) may contribute to the high relapse rates for people who try to stop taking addicting drugs.
It is also now clear that withdrawal syndromes need not be dramatic or life-threatening to play a role in perpetuating drug-using behavior and in relapse after drug withdrawal. Until recently, for instance, experts argued that there was no tobacco withdrawal syndrome. It has now become apparent that while no one has ever died from abruptly quitting the use of tobacco, there is a nicotine withdrawal syndrome that consists of irritability or anger, anxiety, dysphoria, difficulty concentrating, insomnia, and weight gain. It is also clear that the syndrome contributes to relapse because treatment with pharmaceutical nicotine (patches or gum) alleviates withdrawal and reduces the rate of relapse. Similarly, withdrawal from cocaine or amphetamines is not particularly dramatic, but the persistent dysphoria and fatigue probably contribute significantly to relapse after a period of abstinence.
Since drug dependence results from a complex interplay of many factors, it is possible to intervene in a variety of ways. As a result, a number of distinct treatments have evolved, each emphasizing the importance of changing one or more of the contributory factors. One of the most accessible is the 12-step approach, developed initially by Alcoholics Anonymous, which combines spiritual, psychological, and peer support principles, offering mutual help in a nonprofessional environment. Similar 12-step programs have now evolved to treat opioid and cocaine dependence. For people with alcohol dependence, studies have shown that treatments aimed at encouraging patients to attend AA are comparable in efficacy to cognitive behavioral therapy and to professionally delivered treatments designed to enhance motivation.
For many years, researchers have tried to develop useful medications for treating dependence. Many medicines are effective in controlling acute withdrawal syndromes, but relatively few are useful afterward to help avoid relapse. For tobacco (nicotine) dependence, nicotine patches and gum can increase the likelihood of initial abstinence and decrease the chances of relapse. Bupropion (Zyban), a drug developed for depression, is also effective in decreasing relapse rates. For alcohol dependence, opioid antagonists can reduce the likelihood of relapse to heavy drinking, but they do not increase the likelihood of continuous abstinence; the next section discusses specific medications for alcohol. There are as yet no useful medications for cocaine, amphetamine, anxiolytic, or cannabis dependence.
Two distinct types of medications have been approved for the treatment of opioid dependence. Opioid antagonists, such as naltrexone and nalmefene, have been used to help addicts avoid relapse. Antagonists act by displacing the opioids from their action sites on receptors. Therefore, they cannot be given until a person is completely withdrawn from opioids; otherwise, they would cause severe withdrawal. By occupying the opioid receptors, antagonists prevent opioids from producing their typical effects. When people can be persuaded to take these medications, they have a better chance of avoiding rapid relapse.
Opioid agonists are the second type of approved medication: methadone, LAAM, buprenorphine. These drugs are now used throughout the world to treat people with opioid (usually heroin) dependence. When used in adequate doses, these drugs reduce or prevent the euphoric effects of other opioids and reduce people’s craving. Users can function normally once they develop tolerance to these opioid agonists. Since the drugs are themselves opioids, users are physically dependent on them and will experience opioid withdrawal if they stop taking them. But such treatment reduces the use of illicit opioids and thereby reduces the likelihood of adverse consequences associated with such use, such as crime, HIV infection, and overdose deaths.
For many people with typical drug-dependence problems, the toxic effects of the drugs themselves or the conditions under which they are used substantially increase the chances for serious illness, disability, and death. Even people dependent on legally available tobacco and alcohol will have their lives shortened if their dependence persists for long periods. Cigarette smoking can cause lung and other cancers, heart disease, and noncancerous lung disease. High levels of alcohol consumption can cause liver disease, damage to the nervous system, and higher risk of certain kinds of cancers, auto accidents, and injuries. The use of illicit drugs such as cocaine and heroin is associated with even higher risks of premature death, most commonly from accidental overdoses but also from the effects of infections with the AIDS virus (HIV) or hepatitis viruses that result from sharing needles or engaging in unprotected sex.
Many factors influence the likelihood of successful recovery from drug dependence. Much depends on the drugs involved and the circumstances and characteristics of the individual. Sometimes stopping for a while may require little in the way of formal treatment, as when a longterm cigarette smoker finally decides to quit after an illness. Many people with alcohol dependence have found support through such self-help groups as Alcoholics Anonymous. Some people who quit in this way are able to stay free of drugs for very long periods. More typically there are slips and relapses.
Many experts believe that a person who has been severely dependent on a drug, whether alcohol, opiates, tobacco, or cocaine, cannot ever again use that drug, even occasionally, without a high risk of rapidly becoming dependent on it. The basis for the persistent vulnerability of people who were formerly drug-dependent is not clear. It may be that the same genetic or psychiatric factors that contributed to a person’s initial vulnerability still influence his or her behavior, or it may be due to long-lasting changes in neurons during the earlier period of active drug use.
For many people, however, the chances of long term success go up with repeated efforts to end dependence. After several years of continuous abstinence from a drug, the likelihood of relapse becomes relatively low. Although once a person stops taking a drug, many of the toxic effects of drug dependence are largely reversible, some, such as severe liver damage from alcohol use or lung damage from smoking, may persist indefinitely.
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