An Addiction Science Network Resource
What is drug addiction? Considerable confusion exists regarding the
nature of addiction. The most common misunderstanding is that addiction refers
to a state of physical dependence on a drug whereby discontinuing drug intake
produces a withdrawal syndrome consisting of various somatic disturbances. Addiction
is better defined as a behavioral syndrome where drug procurement and use
seem to dominate the individual’s motivation and where the normal constraints
on behavior are largely ineffective. This condition may or may not be
accompanied by the development of physical dependence on the drug. This condition
has also been described as a "psychological" addiction (thus
distinguishing it from physical dependence archaically termed
"physical" addiction), but confusion is minimized by using the term
addiction to refer to the behavioral syndrome described above and the term
physical dependence to refer to the condition associated with somatic
withdrawal reactions. The distinguishing feature of the condition commonly referred
to as addiction is the ability of the drug to dominate the individual’s
behavior, regardless of whether physical dependence is also produced by the
drug.
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What causes drug addiction? Many factors influence a person’s initial
drug use. Personality characteristics, peer pressure, and psychological stress
can all contribute to the early stage of drug abuse. These factors are less
important as drug use continues and the person repeatedly experiences the
potent pharmacological effects of the drug. This chemical action, which
stimulates certain brain systems, produces the addiction, while other
psychological and social factors become less and less important in influencing the
individual’s behavior. When the pharmacological action of a drug dominates the
individual’s behavior and the normal psychological and social control of
behavior is no longer effective, the addiction is fully developed. This
self-perceived "loss of control" is a common feature of drug
addiction and reflects the biological nature of the problem.
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How is drug addiction related to "normal" behavior?
Specialized brain systems have evolved to ensure survival of the species. These
systems direct behavior by rewarding actions that promote survival of the
individual and of the species. Intake of nutrients and procreation are governed
by specific brain systems; for example, the interaction of various substances
in foods (e.g., sugars, fats) activate taste receptors which in turn activate
brain reward mechanisms. Activation of brain reward systems produces changes in
affect ranging from slight mood elevation to intense pleasure and euphoria, and
these psychological states help direct behavior toward natural rewards. Some
chemicals activate brain reward systems directly, bypassing the sensory
receptors mediating natural rewards. The caffeine from coffee and tea, the
alcohol from fermented beverages, and the nicotine from tobacco all activate
brain reward mechanisms directly. Moderate use of these substances has gained
widespread acceptance over the centuries, although their use has been
periodically prohibited (e.g., alcohol during prohibition) or restricted (e.g.,
cigarette smoking currently). Other drugs much more potently activate brain
reward systems. Initial use of these substances is usually accompanied by mood
elevation and other affective changes that lead to their recreational use.
(Some drugs have actions that produce other desirable psychological effects,
such as relaxation.) Much like moderate caffeine and alcohol use, addictive
drugs activate brain reward systems. But the activation is much more intense
causing the individual to crave the drug and to focus their activities around
taking the drug. The ability of addictive drugs to strongly activate brain
reward mechanisms and their ability to chemically alter the normal functioning
of these systems can produce an addiction.
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What are psychoactive drugs? Many drugs interact with brain
mechanisms involved in affect, cognition, and behavior. These compounds are termed
psychoactive drugs. Drugs are usually classified according to their primary
therapeutic actions. Antipsychotic drugs are used to treat schizophrenia and
produce a normalization of the disordered thought processes associated with
this illness. Antidepressant drugs are used to treat psychological depression
and produce a normalization of disturbed affective states characteristic of
depression. And antianxiety drugs (i.e., anxiolytics) are used to treat anxiety
and produce a calming action in nervous individuals. These and numerous other
drugs have important clinical uses and have revolutionized the treatment of
many mild to severe mental disorders. Some work at the ASnet and its laboratory
facility—the Addiction Research Unit (ARU) at the University at Buffalo—investigates
the actions of these drugs, but research focuses on psychoactive drugs that are
addictive. Recent work has also investigated the effects of mildly psychoactive
compounds found in over-the-counter medicines (e.g., pseudoephedrine, diphenhydramine)
and compares their effects with prototypic addictive drugs (e.g., cocaine,
heroin). This comparison helps sharpen the distinction between addictive and
nonaddictive substance use and is used in comparing the effects of other
commonly used substances (i.e., caffeine, nicotine).
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Why conduct basic scientific research? Although the basic biological actions of some drugs are well understood, many important questions remain to be answered. Why do individuals differ in their vulnerability to addiction? How do psychological factors such as stress interact with brain mechanisms to influence the development of an addiction? And why are some people successful in overcoming their addiction while others are not? (Certainly differences in treatment approaches do not account for the successes, because no single treatment program has a uniquely high success rate.) These and many other questions need to be answered. Considerable progress has been made during the past two decades, but considerable more work needs to be done before drug addiction is fully understood. And understanding addiction is the key to successful treatment.
What is the most effective approach to conducting basic research in drug
addiction? Two important considerations direct research at ASnet into basic
mechanisms of drug addiction. First, research focuses on prototypic addiction
drugs. These are drugs with a high addiction liability (i.e., addiction
develops quickly and in a high percentage of individuals after relatively brief
use). Prototypic addictive drugs also have well-defined actions on biological
systems (i.e., interact with specific brain systems) and have historically
shown epidemic patterns of abuse (i.e., abuse patterns showing rapid increases
in the number of people using the drug during the past century often followed
by a marked decline in use; a cyclic pattern of abuse). The two drug classes
that clearly fit these criteria for prototypic addictive drugs are the
psychomotor stimulants (e.g., amphetamine, cocaine, methamphetamine) and the
opiates (e.g., heroin, morphine). Second, animal models are used to study the
underlying biological mechanisms of addiction. Laboratory animals voluntarily
self-administer these prototypic addictive drugs, and basic research in drug
addiction uses animal models to study the biological mechanisms underlying
addiction. (Contrary to popular belief, laboratory animals exposed to addictive
drugs usually remain healthy and suffer no adverse effects of these drugs
[i.e., low morbidity]. The only experiments where research animals are
subjected to any appreciable discomfort involve those studying the effects of
psychological stress or continuous exposure to drugs. Few experiments are
conducted at the ARU investigating these experimental conditions, and all
studies are conducted with laboratory rats.) As basic research studying
prototypic addictive drugs in animal models progresses, the principles learned with
this approach are extended to other addictive drugs (e.g., alcohol) and to
clinical studies (e.g., the treatment of drug addicts).
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Are there other benefits from studying addiction? Understanding the underlying neural basis of addiction opens the door to not only treating specific drug addictions but to also understanding fundamental relationships between behavior and brain function. Addiction presents a situation where chemical activation of brain mechanisms control the individual's behavior, and understanding this process helps delineate processes involved in normal behavior. In addition, several mental disorders, such as schizophrenia and depression, involve disturbances in the same brain system as that involved in addiction. Basic research provides the key to deciphering the biological basis of addiction and to understanding other types of psychopathology.
Why develop medications for treating addiction? Drug addiction involves disturbances in brain chemistry caused by repeated use of certain psychoactive substances. Although the exact nature of these disturbances is not well understood (and hence, the need for continued basic research), the biological nature of this problem is appreciated by most specialists. Psychological counseling and therapy can help the individual recovering from addiction, but the main problem lies with altered brain chemistry that needs to be treated pharmacologically. A number of medications are currently being investigated in various laboratories, but none are yet very effective. Basic research studying prototypic addictive drugs in animal models can identify the neural mechanisms underlying addiction. This information can then direct the development of medications for the treatment of addiction. These medications are evaluated for their safety and effectiveness using animal models before being prescribed clinically to treat addiction. (This last step is particularly important, considering that heroin was originally developed as a treatment for morphine addiction.)
What's wrong with the current sources of information regarding addiction?
A number of agencies and organizations disseminate information about drug
addiction (for examples, see the Links on the ASNet home page). Most notably, the
National Institute on Drug Abuse (NIDA) has been the premier clearing house for
information on drug abuse. Many excellent research monographs, pamphlets, and
press releases are sponsored by NIDA, but this government organization must
also respond to the political realities of all government organizations. When
marijuana use in the late 1940s became a national concern, the government was
involved in producing a film entitled Reefer Madness to
"educate" the public about the dangers of marijuana use. This film
remains a classic today, but not as a testimony to unbiased presentation of
scientific evidence; rather; this film exemplifies the propaganda expounded by
a politically directed organization and has fostered the distrust that many
young people have of government information. More recently, NIDA diverted
attention from cocaine and heroin addiction when the Surgeon General declared
"nicotine more addictive than cocaine." Although this assertion seems
to have been quietly accepted by many scientists, the ASnet considers this
statement unsubstantiated by the empirical data and socially irresponsible.
Dissident opinion has been silenced by the feared repercussions of challenging
official government policy. Other, nongovernment organizations providing
information regarding drug abuse also have hidden agendas. Most are linked with
treatment centers, pharmaceutical firms selling a product, or supported by
government grants and contracts. Much of the information disseminated from
these sources is accurate, but some of it is not. Although the ASnet is in principle
opposed to any illicit substance use, it follows the dictum that unbiased
scientific information should be provided to the public. It is the
responsibility of science to provide the facts of the individual to decide how
to use those facts.
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