9.1 Introduction and Overview
This section covers substance dependence and substance abuse, with descriptions of the clinical phenomena associated with the use of 11 designated classes of pharmacological agents: alcohol; amphetamines or similarly acting agents; caffeine; cannabis; cocaine; hallucinogens; inhalants; nicotine; opioids; phencyclidine (PCP) or similar agents; and a group that includes sedatives, hypnotics, and anxiolytics. A residual 12th category includes a variety of agents not in the 11 designated classes, such as anabolic steroids and nitrous oxide.
A perennial debate in the United States relates to the most effective way to handle drug problems. In the past few years, a small but growing number of government officials, commentators, and academics have argued that the present policy of aggressively prosecuting drug sellers and users should be reconsidered. They have compared the current drug policy with the prohibition of alcohol from 1920 to 1934 and have argued that abolishing drug laws would eliminate the profit motive, the gangs, and the drug dealers. Although she stopped short of endorsing such a radical reversal of the nation’s drug policy, former U.S. Surgeon General Joycelyn Elders, M.D. (served from 1993 to 1994), recommended that the government study the possibility of legalizing drugs of abuse and suggested that doing so might reduce the incidence of violent crimes.
TERMINOLOGY
The concept of substance dependence has had many officially recognized and commonly used meanings over the decades. Two concepts have been used to define aspects of dependence: behavioral and physical. In
behavioral dependence, substance-seeking activities and related evidence of pathological use patterns are emphasized, whereas
physical dependence refers to the physical (physiological) effects of multiple episodes of substance use. In definitions stressing physical dependence, ideas of tolerance or withdrawal appear in the classification criteria (
Table 9.1-1). The term
intoxication is used for a reversible, nondependent experience with a substance that produces impairment (
Table 9.1-2).
Somewhat related to dependence are the words addiction and addict. The word addict has acquired a distinctive, unseemly, and pejorative connotation that ignores the concept of substance abuse as a medical disorder. Addiction has also been trivialized in popular usage, as in the phrases TV addiction and money addiction. Although these connotations have helped the officially sanctioned nomenclature to avoid use of the word addiction, common neurochemical and neuroanatomical substrates may be found among all the addictions, whether to substances or to gambling, sex, stealing, or eating. These various addictions may have similar effects on the activities of specific reward areas of the brain, such as the ventral tegmental area, the locus ceruleus, and the nucleus accumbens.
Psychological dependence, also referred to as habituation, is characterized by a continuous or intermittent craving for the substance to avoid a dysphoric state.
When making a diagnosis, clinicians should specify whether symptoms of physiological abuse or dependence are present (
Tables 9.1-3 and
9.1-4) and also determine whether the disorder is in full or partial remission. The text revision of the fourth edition of the
Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR) allows clinicians to record the current state of the substance dependence by providing a list of course modifiers. A summary of key terms related to dependence and abuse is provided in
Table 9.1-5.
EPIDEMIOLOGY
The National Institute of Drug Abuse (NIDA) and other agencies, such as the National Survey of Drug Use and Heath (NSDUH), conduct periodic surveys of the use of illicit drugs in the United States. As of 2004 an estimated 22.5 million persons over the age of 12 years (about 10 percent of the total U.S. population) were classified as suffering from a substance-related disorder. Of this group, about 15 million were dependent on or abused alcohol.
In 2004, 67.8 percent (0.3 million) persons were dependent on or abused heroin; 17.6 percent (4.5 million) abused marijuana; 27.8 percent (1.6 million) abused cocaine; and 12.3 percent (1.4 million) were classified with dependence on, or abuse of, pain relievers.
With regard to age at first use, those who started to use drugs at an earlier age (14 years or younger) were more likely to become addicted than those who started at a later age. This applied to all substances of abuse, but particularly alcohol. Among adults aged 18 years or older who first tried alcohol at age 14 years or younger, 17.9 percent were classified as alcoholics compared with only 4.1 percent who first used alcohol at age 18 years or older.
Rates of abuse also varied according to age. The rate for dependence or abuse was 1.3 percent at age 12 years, and rates generally increased until the highest rate was reached (25.4 percent) at age 21 years. After age 21 years, a general decline occurred with age. By age 65 years, only about 1 percent of persons had used an illicit substance within the past year, which lends credence to the clinical observation that addicts tend to “burn out” as they age.
More men than women used drugs; the highest lifetime rate was among American Indian or Alaska Natives; whites were more affected than blacks; those with some college education used more substances than those with less education; and the unemployed had higher rates than those with either part-time or full-time employment.
Rates of substance dependence or abuse varied by region in the United States. Rates were higher in the Midwest and West than in the Northeast and South. Rates were also higher in large metropolitan counties than in small metropolitan counties and were lowest in completely rural counties. Rates were also higher among persons on parole or on supervised release from jail (40.8 percent vs. 9.2 percent). A continued need exists for programs to reduce the number of persons driving while under the influence of drugs or alcohol. The percentage of drivers who admitted driving under the influence of alcohol at some time during the past year increased from 10 percent in 2000 to 13.5 percent in 2004, and those driving under the influence of drugs increased from 3.1 percent to 6 percent during the same period. A comprehensive survey of drug use and trends in the United States is available at http://www.samhasa.gov.
ETIOLOGY
The model of drug dependence conceptualizes dependence as a result of a process in which multiple interacting factors influence drug-using behavior and the loss of flexibility with respect to decisions about using a given drug. Although the actions of a given drug are critical in the process, it is not assumed that all people who become dependent on the same drug experience its effects in the same way or are motivated by the same set of factors. Furthermore, it is postulated that different factors may be more or less important at different stages of the process. Thus, drug availability, social acceptability, and peer pressures may be the major determinants of initial experimentation with a drug, but other factors, such as personality and individual biology, probably are more important in how the effects of a given drug are perceived and the degree to which repeated drug use produces changes in the central nervous system (CNS). Other factors, including the particular actions of the drug, may be primary determinants of whether drug use progresses to drug dependence, whereas still others may be important influences on the likelihood that drug use leads to (1) adverse effects or (2) successful recovery from dependence.
It has been asserted that addiction is a “brain disease,” that the critical processes that transform voluntary drug-using behavior to compulsive drug use are changes in the structure and neurochemistry of the brain of the drug user. Sufficient evidence now indicates that such changes in relevant parts of the brain do occur. The perplexing and unanswered question is whether these changes are both necessary and sufficient to account for the drug-using behavior. Many argue that they are not, that the capacity of drug-dependent individuals to modify their drug-using behavior in response to positive reinforcers or aversive contingencies indicates that the nature of addiction is more complex and requires the interaction of multiple factors.
Psychodynamic Factors
The range of psychodynamic theories about substance abuse reflects the various popular theories during the past 100 years. According to classic theories, substance abuse is a masturbatory equivalent (some heroin users describe the initial “rush” as similar to a prolonged sexual orgasm), a defense against anxious impulses, or a manifestation of oral regression (i.e., dependency). Recent psychodynamic formulations relate substance use as a reflection of disturbed ego functions (i.e., the inability to deal with reality). As a form of self-medication, alcohol may be used to control panic, opioids to diminish anger, and amphetamines to alleviate depression. Some addicts have great difficulty recognizing their inner emotional states, a condition called alexithymia (being unable to find words to describe their feelings).
Learning and Conditioning.
Drug use, whether occasional or compulsive, can be viewed as behavior maintained by its consequences. Drugs can reinforce antecedent behaviors by terminating some noxious or aversive state such as pain, anxiety, or depression. In some social situations, the drug use, apart from its pharmacological effects, can be reinforcing if it results in special status or the approval of friends. Each use of the drug evokes rapid positive reinforcement, either as a result of the rush (the drug-induced euphoria), alleviation of disturbed affects, alleviation of withdrawal symptoms, or any combination of these effects. In addition, some drugs may sensitize neural systems to the reinforcing effects of the drug. Eventually, the paraphernalia (needles, bottles, cigarette packs) and behaviors associated with substance use can become secondary reinforcers, as well as cues signaling availability of the substance, and in their presence, craving or a desire to experience the effects increases.
