C H A P T E R
4 Addictions and AddictiveBehaviors Tobacco surely was designed To poison and destroy mankind.
—Philip Freneau, 1786
Thou hast the keys of Paradise, O just, subtle, and mighty opium! —Thomas De Quincey, 1821
■ Some feelings and the substances or activities that produce them are so motivating that little else seems to matter. This observation, along with the following questions, can guide an understanding of the concepts in this chapter:
1. What can drugs of abuse, electrical stimulation, and exercise tell us about the brain as a source of motivation?
2. How do drugs differ from natural incentives in motivating behavior?
3. Why are there pleasure centers in the brain and how do they work?
4. What are the psychological theories for starting and maintaining drug use?
5. Why do strenuous exercise and gambling become addictive behaviors?
Drugs of Abuse and Addiction A young man has just left his mother’s apartment and is strolling around his old neighbor- hood. He is delighted to be free after having been in prison for one year. While walking, he reflects on the time he spent there undergoing heroin detoxification. This very unpleasant process left him free of any drug cravings. As he walks along familiar streets and sees familiar buildings, however, his intestines begin to rumble, his eyes begin to water, and he starts yawning. He also begins to sweat and becomes nauseated, as symptoms of his old withdrawal agony start returning. These are symptoms that he has not experienced for over a year. “How is this possible?” he asks himself. “I haven’t felt this way for so long.” Although feeling panicky and anxious, he knows how to alleviate this old sickness. He turns the corner and begins walking toward a familiar apartment building where relief awaits.
A young woman drives her car uptown to visit her girlfriend. Inside her friend’s apart- ment she notices a mirror lying face up on the coffee table. She can’t take her eyes off the mirror; it elicits a mounting excitement in her that seems to take over her body. Does her
Motivation: Biological, Psychological, and Environmental, Third Edition, by Lambert Deckers. Published by Allyn & Bacon. Copyright © 2010 by Pearson Education, Inc.
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friend have any cocaine, she wonders? Her whole body tingles in delightful waves of antici- pation. She can almost taste the cocaine at the back of her throat. “If I am feeling a rush just from seeing this mirror, why do I bother using cocaine at all?” she thinks. The reason, she an- swers herself, is that there is no substitute for the drug. “Nothing in any way, shape, or form can make me feel this good.”
The purpose of this section is to describe the effects of selected legal and illegal psy- choactive drugs, how they differ from natural incentives, and why people are motivated to use them. A psychoactive drug is any chemical substance that alters a person’s mood and behavior as a result of the drug’s effect on the function of the brain.
Psychoactive Drugs People are motivated to consume psychoactive drugs because the immediate pleasurable re- sults seem to outweigh the long-term negative consequences. The drugs described in this section are controlled substances, which means their manufacture, possession, and distri- bution are regulated by the federal government of the United States. The only exception is caffeine, which may even be used by children in soft drinks.
Caffeine. “Caffeine is the most widely consumed psychoactive substance in the world” (Strain & Griffiths, 2005, p. 1201). It is consumed in coffee, tea, chocolate, sodas, and en- ergy drinks. Caffeine has a stimulating effect that is deemed pleasurable especially among caffeine drinkers. Even when caffeine is disguised in a novel fruit tea or in capsule form, consumers report feeling more alert, energetic, lively, and clear-headed, and experience greater well-being (Schuh & Griffiths, 1997; Yeomans et al., 1998). Furthermore, fruit tea and juice that contain caffeine are preferred more than those same liquids without caffeine especially for individuals who are caffeine deprived (Yeomans et al., 1998). Common caf- feine withdrawal symptoms begin 12 to 24 hours after the last caffeine drink. The symp- toms include headache, fatigue, decreased energy, depressed mood, and decreased alertness (Juliano & Griffiths, 2004).
Alcohol. Ethanol is the alcohol in a drink. It consists of carbohydrates that serve as the active ingredient in beer, wine, and distilled spirits (whiskey, vodka, rum, gin). The amount of alcohol that reaches the brain depends on a number of factors, including the drinker’s body size, whether the stomach is empty or full, and whether other liquids are also being taken. Although the size of a typical drink may vary, the alcohol content remains constant. That is, about 0.5 ounces of alcohol is contained in a 12-ounce mug of beer, a 4-ounce glass of wine, and a 1.25-ounce cocktail of 80-proof liquor (Fishbein & Pease, 1996). At low amounts, alcohol produces good feelings, such as euphoria, and re- leases inhibitions. This can result in increased talkativeness, aggression, belligerence, and promiscuity.
Nicotine. Tobacco use in the form of cigarettes, cigars, pipes, and smokeless tobacco de- livers nicotine to the brain. Nicotine is the major psychoactive drug in tobacco. In addition to nicotine, however, smoke contains ammonia (an ingredient in kitchen cleaners), arsenic (rat poison), and cyanide (a very deadly poison with the smell of bitter almonds). Some cig- arette packs inform users that smoke gives off carbon monoxide, a colorless, odorless,
Motivation: Biological, Psychological, and Environmental, Third Edition, by Lambert Deckers. Published by Allyn & Bacon. Copyright © 2010 by Pearson Education, Inc.
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highly poisonous gas that prevents the blood from utilizing oxygen. A person’s initial reac- tion to smoking is quite negative, including coughing, dizziness, nausea, and vomiting. These symptoms eventually disappear, and seasoned smokers report that smoking is mood enhancing and relaxing. If a person tries to quit smoking after becoming addicted, she ex- periences a set of negative symptoms, including irritability, restlessness, anxiety, depres- sion, hostility, difficulty concentrating, and hunger (Fishbein & Pease, 1996).
Amphetamines. Originally a form of this stimulant was available from the khat plant but now it is produced synthetically from various chemicals. Known by street names like speed and crystal meth (or ice), amphetamines produce alertness, euphoria, and well-being more effectively than does cocaine (Jaffe et al., 2005). Methamphetamine is derived from am- phetamine and produces even greater psychoactive effects. Ecstacy is a drug similar to methamphetamine. It is one of the more commonly used hallucinogenic drugs, and is es- pecially notable on university campuses (Goldstein, 2001). When taken orally in capsule or tablet form, an ecstacy-produced high can last five hours and includes feelings of spiritual- ity and closeness (Schuckit, 2000).
Cannabis. This category of psychoactive drugs includes marijuana and hashish. Tetrahy- drocannibol (THC) is the psychoactive component of these drugs and is derived from hemp (cannabis) plants. Smoking marijuana produces a “high” that includes feeling euphoric, re- laxed, drowsy, and experiencing a dreamlike state of disconnectedness from the world (Goldstein, 2001). Withdrawal symptoms after heavy marijuana use have included fatigue, anxiety, concentration problems, yawning, change in appetite, depression, and sleepless- ness (Schuckit, 2000).
Cocaine. Coca paste is derived from the leaves of the coca plant found in South America. Cocaine (cocaine hydrochloride) is the odorless white powder that is processed from coca paste. Crack cocaine is made by mixing cocaine hydrochloride with water and bak- ing soda. When the water evaporates, the mixture turns into a crystalline lump that is smoked in a special pipe. Some of the positive effects felt from cocaine include euphoria, increased sense of energy, increased mental acuity and sensory awareness, and a “full body orgasm” (Gold, 1992). These effects are short-lived, often lasting just 15 to 30 minutes. Abusers often go on cocaine binges, which means that they indulge in extremely high use for a day or two, only quitting when their drug supply runs out. During a binge, tolerance quickly develops, and when the effects of cocaine wear off, a person “crashes,” experienc- ing negative symptoms such as depression and anxiety and the need for sleep (Gawin & Kleber, 1986).
Opiates. Opium is obtained from the sap that comes from the seed of the opium poppy. This sap is processed into opiates, such as morphine, codeine, and heroin. Morphine and codeine serve as painkillers and are also used to treat diarrhea and coughs. Heroin is an even more potent drug derived from opium. Opiate users experience a “rush,” which has been likened to sexual orgasm. In addition, there is an elevation of mood (“a high”), a sense of euphoria, a decrease in anxiety, and an increase in self-esteem (Jaffe, 1992). Swallowing is one route of opiate ingestion but not because of any taste that it provides.
Motivation: Biological, Psychological, and Environmental, Third Edition, by Lambert Deckers. Published by Allyn & Bacon. Copyright © 2010 by Pearson Education, Inc.
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2002 2003 2004 2005 2006
FIGURE 4.1 First-Time Drug Use. The estimated number of individuals age 12 years or older who tried various drugs for the first time during the 2002 to 2006 period. Cannabis includes mari- juana and hashish.The method of recording methamphetamine use for 2006 changed and is not com- parable to previous years.
Source: Table G.26, SAMSHA, Office of Applied Studies, National Survey on Drug Use and Health, 2002–2006. http://www.oas.samhsa.gov/NSDUH/2k6NSDUH/AppG.htm. Methamphetamines data comes from Table 8.46 at http://oas.samhsa.gov/nsduh/2k6nsduh/tabs/Sect8peTabs46.pdf
Extent of Drug Use Annual surveys help indicate the extent people are motivated to experiment, use, and even- tually abuse psychoactive drugs. The National Survey on Drug Use and Health tracks yearly trends in the use of many psychoactive drugs. Figure 4.1 shows the number of people 12 years or older who had their first drug experience during the years 2002 to 2006. The most frequently tried drug is alcohol followed by cigarettes. Heroin is experimented with least frequently. A certain percentage of the individuals in Figure 4.1 will become addicted to the drug or drugs with which they experimented. The reason for people’s experimenta- tion and subsequent addiction are many and will be described in this chapter.
➣ More extensive statistics on psychoactive drug use can be obtained at http://www.oas. samhsa.gov
Characteristics of Addiction This initial experimentation occurs for various reasons and for any pleasures the drugs produce. From this point forward, however, some individuals will stop, continue to use occasionally, or become involuntarily addicted. For instance, following experimentation with smoking or drinking alcohol, some people quit or continue to use in moderation, as in social drinking or occasional smoking. However, others become involuntarily addicted
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10 20 30 40 50 60 70 80 90 100 110
FIGURE 4.2 Drug Tolerance. Patterns of opiate intake in a human under conditions of continuous drug avail- ability. The graph shows the amount of the drug taken over consecutive days.
Source: From “Similarities in Animal and Human Drug-Taking Behavior” by R. R. Griffiths et al. (figure 3, p. 17), 1980, in N. K. Mello, Ed., Advances in Substance Abuse, Greenwich, CT: JAI Press. Copyright 1980 by JAI Press, Inc. Reprinted by permission.
and develop intense uncontrollable cravings for the drug and cannot stop using it. Let us examine the characteristics of drug addiction: craving, tolerance, and the unpleasantness of withdrawal.
Craving. Do you eat because you want to get rid of your hunger or because you want to attain the pleasure derived from delicious food? Craving is an almost overpowering, uncontrollable urge for the drug the person has been using. However, is craving the desire to rid oneself of the negative symptoms associated with withdrawal or is craving the desire for the strong euphoric effect a drug provides? To find an answer to this question, drug researchers asked alcohol, opiate, and cocaine patients what the feeling of craving meant to them. Their answer seemed to depend on the drug the patient chose. For alcoholics and opi- ate patients, craving was associated more with getting rid of negative withdrawal symptoms and less with any positive feelings the drug may have provided. However, for cocaine patients, the pattern of findings was reversed. For them craving was associated more with getting the positive feelings derived from cocaine and less with removing negative feelings (Childress et al., 1992). Thus, on the whole, craving seems linked to reducing unpleasant feelings or negative drug effects as well as with a desire to experience a drug’s specific euphoric effects.
Tolerance and Withdrawal. Drug addiction or dependence is addressed in the Diagnostic and Statistical Manual of Mental Disorders of the American Psychiatric Association (2000), which states that drug dependence is characterized by tolerance and withdrawal. Tolerance means that the body habituates to the effects of a drug because of repeated experiences. Tolerance is a case of stimulus (drug) habituation and is manifested as an increase in the amount of drug dosage needed to achieve the same desired effect. Figure 4.2 shows increased dosages
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needed to offset the tolerance developed by a human addicted to morphine (Griffiths et al., 1980). The data in Figure 4.2 come from a study by Wikler of an individual with a history of drug abuse (cited in Griffiths et al., 1980, p. 17). This individual was allowed to request any drug as often and in any amount he wished. He chose intravenous morphine injections for 112 consecutive days, after which he was instructed to detoxify himself.
A withdrawal syndrome is a second characteristic of drug dependence. It refers to a drug-opposite effect. A drug produces a rush or pleasant experience. However, when the drug wears off a person experiences feelings that are by contrast the opposite and negative of what the drug initially produced. Withdrawal can range from mild to extreme and depend on the length of time since the last drug use. Caffeine withdrawal may result in a headache and lack of energy while opiate withdrawal may involve dysphoria, depressed mood, nau- sea, and feelings of distress. In addition, there are increased cravings for the drug that pro- duced the withdrawal.
Additional characteristics of drug dependence involve an inordinate amount of time spent in obtaining the substance at the expense of other activities, unsuccessful attempts to reduce consumption, and continued use despite resulting physical and psychological prob- lems. The everyday term addiction is usually employed in place of the term dependence. Addiction has come to mean an intense craving, seeking out, and use of a particular drug. Extended drug use may be accompanied by abuse, which involves the inability to maintain social roles such as family, school, or work. It involves drug use in dangerous situations, such as drunk driving or sharing needles. Drug abuse continues in spite of legal problems and persistent interpersonal problems, such as arguments at home. These characteristics of abuse may become part of addiction in which use of a particular drug occurs in spite of the adverse physical and social consequences that result.
Initiation into Drug Use Why do a percentage of individuals who experimented with drugs become dependent on them? Genetic dispositions, personality traits, and a condition known as reward deficiency syndrome all seem to contribute to an individual’s tendency to become addicted.
Genetic Disposition. “Everyone in my family smokes” and “Alcoholism runs in my family” are observations that imply a genetics of addiction. This field employs methods from behavioral genetics in order to determine how people’s genetic inheritance determines their susceptibility to move from experimentation to addiction. Behavioral genetics is based on the assumption that drugs have their effects on structures in the brain. These structures are genetically transmitted from one generation to the next. Furthermore, greater genetic similarity between two individuals is associated with greater similarity in their brains and nervous systems, which in turn is associated with corresponding resemblances in their vulnerability to drugs of abuse (Goldman et al., 2005; Plomin et al., 2001).
Genetic evidence indicates that dependence on the substances in Figure 4.1 are heri- table (Kendler et al., 2003; Li et al., 2003) as is dependence on caffeine and gambling (Goldman et al., 2005; Lessov et al., 2004). Heritable means that as the genetic similarity between individuals increases, their similarity in drug-use habits increases. However, genes do not imply that a person is destined to become addicted to psychoactive drugs. In addition
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to the effects of genes, the general environment, and environmental effects unique to the individual also contribute to drug dependence (Lessov et al., 2004; Turkheimer, 2000).
Personality Disposition. In addition to examining the genetic dispositions, psycholo- gists have also examined personality traits and their association with drug use. It is impor- tant to note that there is no single addictive personality but that there are several personality traits that are associated with addiction (Ball, 2005). Two such personality traits are sensa- tion seeking and impulsiveness. Sensation seeking refers to a trait that is associated with seeking varied, intense, and novel sensations and the willingness to take various risks to ex- perience those sensations (Zuckerman, 1994). In a review of the literature, Zuckerman (1994) concluded that sensation seekers because of their curiosity and need for novelty seemed motivated to experience a variety of drugs. Disinhibition is a characteristic of sen- sation seeking that seems particularly associated with the use of alcohol and nicotine. Dis- inhibition is characterized by reduced social restraint, which is associated with the tendency to party, gamble, and engage in sexual activities. Hittner and Swickert (2006) in a review of studies on sensation seeking that involved over 37,000 participants discovered that dis- inhibition is the strongest predictor of alcohol use. Nicotine use is also associated with dis- inhibition. Perkins and coresearchers (2000) administered a nasal spray of nicotine to nonsmokers who varied in sensation seeking. The intensity of the individuals’ positive and negative reactions to the spray depended on the level of sensation seeking. Also, individu- als high in disinhibition reacted to the spray with more pleasure, a greater head rush, ten- sion, confusion, and arousal. These differences in the initial reaction to nicotine may help explain why high-sensation seekers are more likely to end up as smokers, compared to low- sensation seekers (Zuckerman et al., 1990).
Impulsiveness is the other personality trait associated with psychoactive drug use. Impulsiveness consists of two components: heightened sensitivity to rewards and lack of foresight and planning (Dawe et al., 2004). Impulsive individuals are more sensitive to the rewarding pleasures that drugs provide. But they are also less aware of any negative conse- quences of their drug use. These two components are responsible for the relationship be- tween impulsiveness and the use of drugs like alcohol, nicotine, and cannabis (Dawe et al., 2004). The Barratt Impulsiveness Scale (Patton et al., 1995) is one method that psycholo- gists use to measure an individual’s degree of impulsiveness. Five items sampled from this 30-item scale are presented in Table 4.1. Impulsiveness is the inverse of self-control as measured by the Brief Self-Control Scale (see Chapter 2; Tangney et al., 2004). Does the Barratt Impulsiveness Scale show a difference between individuals who abuse psychoac- tive drugs and those who do not? It does. Substance abuse patients, for example, scored sig- nificantly higher than did a large sample of university students. Other studies have also indicated that individuals who score higher on the Barratt Impulsiveness Scale are more prone to abuse drugs. For example, patients who became dependent or abused alcohol before and after age 25 were compared on their impulsiveness scores. Individuals who developed alcohol problems prior to age 25 had higher impulsiveness scores than those who developed problems after age 25 (Dom et al., 2006). Smoking is also affected by impul- siveness. Greater impulsiveness in beginning smokers was associated with greater expecta- tions of the positive and negative reinforcing effects of smoking. More impulsive individuals expected smoking to be very pleasurable, would smoke more frequently, and would be less motivated to quit (Doran et al., 2007).
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➣ The complete Barratt Impulsiveness Scale may be found on the website of the International Society for Research on Impulsivity; http://impulsivity.org/BIS-11
Personality traits like sensation seeking and impulsiveness are not psychological ab- stractions but are heritable—that is, they have a genetic basis. Thus, although these per- sonality traits are associated with drug use, they are also under the partial control of our genes (Hur & Bouchard, 1997; Zuckerman, 2002). Genes help contribute to a person’s level of sensation seeking and impulsiveness, which then makes those individuals susceptible to drug experimentation and abuse (Goldman et al., 2005).
The reward deficiency syndrome is another characteristic that may influence drug ex- perimentation and use (Blum et al., 1996, 2000). This syndrome refers to sensory deprivation of the brain’s pleasure area because of a low number of receptors that are sensitive to a neu- rotransmitter known as dopamine (a chemical related to pleasure). Individuals with this syn- drome may also be less sensitive to dopamine when it is released during activities that are pleasurable for most people. The shortage of dopamine pleasure receptors motivates individ- uals to seek out the more intense forms of pleasure that are provided by both illicit and licit drugs and gambling. As a consequence, they are more likely to take drugs and are more likely to become alcoholics, drug abusers, smokers, or compulsive gamblers (Blum et al., 1996, 2000).
Section Recap There are both legal and illegal psychoactive drugs, which are chemical substances that can alter a person’s mood and behavior. Caffeine has a stimulating effect and is the most widely used psychoactive substance in the world. Nicotine is the psychoactive drug found in to- bacco, and alcohol is found in beer, wine, and distilled spirits. Psychoactive drugs include opiates, such as morphine, codeine, and heroin; and cocaine, a powdery substance derived from coca plants. Smoking marijuana arouses feelings of euphoria and drowsiness. Amphetamines and methamphetamines produce alertness, euphoria, and subjective well- being and are seemingly more powerful than cocaine. According to the National Survey on Drug Use and Health of individuals ages 12 years and older, the most frequently tried drug (excluding caffeine) is alcohol and the least frequently tried is heroin.
Drug dependence or addiction is characterized by craving, tolerance, and a with- drawal syndrome. Craving refers to an overpowering, almost uncontrollable urge for the
TABLE 4.1 Items from the 30-Item Barratt Impulsiveness Scale
I “squirm” at plays or lectures. I act on impulse. I plan tasks carefully.* I like to think about complex problems.* I often have extraneous thoughts when thinking.
Source: Adapted from “Factor Structure of the Barratt Impulsiveness Scale” by J. H. Patton et al., 1995, Journal of Clinical Psychology, 51, table 1, p. 771.
Rate how true each item is of you: 1 � rarely/never, 2 � occasionally, 3 � often, 4 � almost always/always. *means reverse score: 1 � 4, 2 � 3. Sum your scores. A higher score means greater impulsiveness.
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drug a person uses in order to obtain the euphoric effects or to reduce withdrawal effects. Tolerance means that a person habituates to the effects of the drug while the withdrawal syndrome refers to a drug-opposite effect that results from drug-use abstinence. Several fac- tors contribute to people’s experimentation and subsequent addiction. According to the genetics of addiction, the likelihood of a person becoming addicted is heritable, which means that an increase in the genetic similarity between individuals is linked to an increase in their similarity of drug use. Personality traits like sensation seeking and impulsiveness are also associated with drug use. The trait of impulsiveness is linked to heightened drug pleasures and a lack of foresight regarding the consequences of drug use. Individuals suf- fering from a reward deficiency syndrome are more likely to become addicted. This syn- drome refers to the brain’s pleasure center being less sensitive to dopamine, a brain chemical that provides the basis for natural rewards.
Theories of Drug Addiction The two fictitious anecdotes that opened this chapter illustrate that psychoactive drugs are powerful motivators. Both individuals in these examples feel the effects of stimuli associ- ated with their drug use. A mirror and familiar buildings evoke feelings linked with antici- pated pleasure and with drug withdrawal. The motivation for drug-seeking behavior comes from the pull of anticipated positive consequences—that is, anticipated positive reinforcers, such as a cocaine high. In the other case, the motivation comes from the push to escape aver- sive withdrawal symptoms—that is, negative reinforcers, such as escape with heroin. Dur- ing the drug experimentation phase, an individual is presumably motivated by anticipated positive reinforcement: drug “highs” or euphoria. It is only after addiction that drugs are used to escape drug “lows” or aversive withdrawal symptoms.
This section presents explanations for the motivation of drug use. The first explana- tion involves reductionism. What happens in the brain that is associated with drug eupho- ria and withdrawal pains? The second explanation involves the association of drug stimuli with pleasurable and aversive feelings that emerge in a person’s consciousness.
Discovery of Pleasure Centers in the Brain In 1953 pleasure centers were discovered in the brain of a rat when James Olds implanted elec- trodes in the hypothalamus. Quite by accident an electrical impulse was delivered while the rat happened to be in a certain location. As a consequence of this stimulation, Olds observed the rat returning to this same location as if it was searching for whatever produced the electrical stimulation (Olds, 1958, 1977). Subsequently, Olds undertook a series of experiments to more closely examine the role of electrical brain stimulation as a reinforcer and as a source of pleasure (Olds, 1958, 1977). Rats were placed in an operant chamber, which is a small cage with a lever on one end. The rats could move freely about the chamber, and when they pressed the lever, a small electrical current was delivered through a chronically implanted electrode, thus stimu- lating that part of their brain. Olds discovered that the rats were very motivated to attain this stimulation, depending on the part of the brain being stimulated.
Pleasure Emerges from the Brain There are several implications from Olds’ discovery that will help us understand the moti- vation that leads to addiction.
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Drugs and Natural Incentive Effects. First, artificially produced psychoactive drugs have the ability to provide pleasurable effects that are unmatched in nature. The ingestion of drugs provides no pleasurable sensory effects like those of natural incentives (Stewart et al., 1984). Only when drugs reach the brain do they have rewarding effects. Certain foods and drinks provide pleasure by their smell and taste, and the touch of the right person is pleasure to our skin. Drugs, however, do not provide pleasure to our taste buds and touch receptors. In fact, their routes of administration can be downright unpleasant. Cocaine pow- der is inhaled into the nose to penetrate the nasal membrane. Hypodermic needles allow addicts to inject drugs (morphine, heroin) directly into their veins for transport to the brain. Nicotine is absorbed into the bloodstream from the lungs when tobacco is smoked. In the 1800s, opium was smoked in specially made pipes, as is crack cocaine today. Alcohol is a drug taken by swallowing and is one that humans flavor heavily. Putting powder up the nose, pricking the skin, and filling the lungs with smoke are unpleasant experiences. Yet, indi- viduals are willing to endure these procedures in order for drugs to reach the brain.
Neurons and Neurotransmitters. A second implication of Olds’s research is the com- pulsive and uncontrollable nature of both brain stimulation and drug use. Perhaps only by examining what occurs in the brain will it be possible to understand the powerful nature of drug addiction. Toward this end, scientists have discovered that identical brain sites are in- volved in electrical stimulation and in the action of psychoactive drugs. Prior to embarking on these implications, it is necessary to provide a brief description of the mechanics and processes of the brain that allow drug-induced pleasure to emerge.
The brain is composed of billions of neurons, which are cells that specialize in con- ducting electrical impulses. Neurons receive external information, process it, and move it along. Neurons represent information as impulses, which are brief electrical changes. Impulses travel along neurons, which are connected to one another in a complex commu- nication network. Neurons come in a wide variety of sizes and shapes, but all contain sev- eral important parts: dendrites, cell body, axon, and terminals (see Figure 4.3). Dendrites receive impulses from sense organs (eyes, ears, nose, touch receptors) or from other neu- rons. If a sufficient number of impulses from the senses or other neurons arrive at the den- drites in a certain period of time, then the neuron fires. The neuron sends its own impulse traveling down its axon to the end, where the axon begins to divide like branches of a tree. These branches end in little knobs known as terminal buttons, which come very close to the dendrites of other neurons without actually touching them (see Figure 4.3). Thus, neu- rons are one-way channels of communication: they receive impulses from the dendrites of sending neurons and then act like receiving neurons. A receiving neuron also becomes a sending neuron, since its nerve impulses are transmitted to other neurons, to glands, or to muscles.
At the end of the terminal button, the nerve impulse comes to a halt because there is a synapse or cleft between the sending neuron and the receiving neuron. It is impossible for the electrical impulse to jump the cleft in order to stimulate the next neuron (see Figure 4.3). This problem is handled by switching from electrical to chemical communication. When the nerve impulse reaches the terminal buttons, it releases a chemical or neurotransmitter from containers known as synaptic vesicles. The molecules of this chemical substance diffuse across the synapse and bind with receptor sites on the receiving neuron (see Figure 4.3). Neu- rotransmitters fit into the receptor sites of the receiving neuron like a key into a lock. When
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FIGURE 4.3 The Neuron and the Nerve Impulse. A nerve impulse travels down the length of the axon from the sending to the receiving neuron. When the impulse reaches the terminal buttons, it re- leases a neurotransmitter, which diffuses across the synapse and binds with the receiving neuron. The neurotransmitters then cause the receiving neuron to fire. Psychoactive drugs travel to synapses and affect neurons directly or indirectly by influencing the neurotransmitters that are already there.
enough neurotransmitter is released and binds with receptor sites, then the receiving neuron will fire its own impulse. Once the neurotransmitter has done its job, it is reabsorbed into the terminal button through a process known as reuptake. The reason for this brief digression into the action of nerve impulses is because drugs of abuse can fire certain neurons that compose areas of the brain called pleasure centers, which are described next.
Common Brain Pathway. Each psychoactive drug has its own specific effect. For ex- ample, cocaine, nicotine, and caffeine stimulate the central nervous system so that people feel excited, energetic, and more alert. Alcohol, in contrast, is a depressant, which means it slows the function of the central nervous system. Alcohol makes a person feel less anxious, lowers stress, lowers social inhibitions, and increases relaxation. In addition, drugs differ in their method of ingestion and hence sensory stimulation—that is, by smoking, drinking, or injecting it. However, drugs also have a common effect, which refers to the pleasurable feelings that they create. These feelings range from mild euphoria to a rush and emerge from neuronal activity in specific areas of the brain.
In spite of their different routes of administration, drugs share a common brain reward system where they produce their general pleasure (Nestler, 2005; Self, 2005; Wise, 2004). This reward system is referred to as the mesolimbic dopamine system, which has two
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characteristics. First, it is composed of neurons in the middle of the brain that connect differ- ent sites, such as the nucleus accumbens and the ventral tegmental area. These two sites are responsible for much of the euphoric effects that come from using drugs. Second, dopamine is the neurotransmitter that fires the neurons that make up the mesolimbic dopamine system. Psychoactive drugs travel to the synapses of neurons in the mesolimbic dopamine system where they either directly stimulate the neurons of the nucleus accumbens and ventral tegmen- tal area or they influence the actions of dopamine that is already there. Drugs cause either the release of dopamine or prevent the reuptake of dopamine. In either case, dopamine increases the level of activity in the system, from which emerges feelings of pleasure and euphoria.
The different psychoactive drugs work various ways to produce their ultimate effects (Kelley & Berridge, 2002; Nestler, 2005; Self, 2005; Wise, 2004). Cocaine works by blocking the reuptake of dopamine into the terminal buttons of axons located in the nucleus accumbens. Hence, dopamine remains constantly available to stimulate the neurons there. Opiates (mor- phine and heroin) act differently than cocaine to produce pleasure. When an opiate is injected into the bloodstream, it reaches the brain and attaches to neurons that use a set of neurotrans- mitters known as opioids (resembling opium). The opioid neurons in turn release the neuronal brake that inhibits the release of dopamine. With the brake off, more dopamine is released, and pleasure is the result. Opiates can also stimulate the nucleus accumbens directly, which also results in feelings of pleasure (Goldstein, 2001; Nestler, 2005; Self, 2005). Drinking moder- ate amounts of alcohol also seems to take the brakes off of the release of dopamine. Nicotine is able to activate the release of dopamine in both the nucleus accumbens and the ventral tegmental area (Nestler, 2005). Thus, cocaine, opiates, alcohol, and nicotine evoke pleasur- able feelings because of their ability to stimulate the mesolimbic dopamine system.
➣ A video of the actions of cocaine is available at http://www.pbs.org/wnet/closetohome/ animation/coca-anim2-main.html
➣ A video of the actions of heroine is available at http://www.pbs.org/wnet/closetohome/ animation/opi-anim2-main.html
It is important to remember the natural function of dopamine and the mesolimbic dopamine system. Recall from Chapter 2 Spencer’s (1899) claim that behavior that is im- portant for survival is pleasurable. Dopamine and the mesolimbic dopamine system help carry out that function for the individual and the species. Dopamine is the neurotransmitter responsible for the reinforcing effects provided by natural rewards, such as food for hungry animals, water for thirsty animals, and the opportunity for sexual intercourse by sexually receptive animals (Wise & Rompre, 1989).
Blocking Drug Effects. If psychoactive drugs could be blocked from binding with their appropriate neurons, then their pleasurable effects should be reduced. Consequently, any behavior motivated by the delivery of those drugs should decline also. This blocking effect is made possible by drugs known as antagonists. Pimozide is an antagonist of dopamine. For example, de Wit and Wise (1977) found injecting rats with pimozide reduced their re- sponsiveness for a cocaine reinforcer. It was as if the antagonist blocked any pleasure that the cocaine provided. Naltrexone is an antagonist of heroin. Stewart and Wise (1992) dis- covered that rats injected with naltrexone exhibited a decline in their lever pressing for a heroin reinforcer. Again, it seems that the antagonist reduced the pleasure that heroin pro- vided. Consequently, the rats’ motivation for heroin declined.
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0 Urge Drinks
FIGURE 4.4 Effects of Naltrexone on Alcohol. Six consecutive days of naltrexone reduced the urge for a drink of alcohol and reduced the number of drinks consumed during a 2-hour period.
Source: Adapted from “Naltrexone Decreases Craving and Alcohol Self-Administration in Alcohol-Dependent Subjects and Activates the Hypothalamo-Pituitary-Adrenocortical Axis” by S. S. O’Malley et al., 2002, Psychopharmacology, 160, table 1, pp. 22, 24.
Naltrexone shows promise in helping humans curb their cravings in order to over- come various addictions (Johansson et al., 2006; O’Brien, 2005). In one experiment, O’Malley and coresearchers (2002) investigated the effects of naltrexone on 18 alcohol- dependent individuals, who consumed 20 to 40 drinks per week. During a 6-day period prior to the experiment, half the participants took either a daily dose of naltrexone while the other half took a daily placebo (non-drug control). Six hours after the last dose, they were tested in a laboratory for their alcohol craving with the Alcohol Urge Questionnaire (Bohn et al., 1995). Next, in order to prime the desire for alcohol, participants were provided drinks of their favorite alcohol mixed with fruit juice. A test for any priming effects required the par- ticipants to make a choice eight times between receiving a drink now or receiving $3 to- morrow. Thus, the participant could consume a maximum of eight drinks or earn up to $24. If naltrexone effectively reduced the reinforcing value of alcohol, then the naltrexone par- ticipants should consume fewer drinks than the placebo participants should. This prediction was confirmed. The results in Figure 4.4 show that naltrexone reduced the urge for a drink and reduced the number of drinks that were consumed. In addition, naltrexone had the effect of making individuals drink more slowly. The researchers concluded that naltrexone re- duced the reinforcing value of alcohol for alcohol-dependent individuals.
➣ The complete Alcohol Urge Questionnaire is available at http://www.ncbi.nlm.nih.gov/ books/bv.fcgi?rid=hstat5.section.51977
Psychological Theories In contrast to explanations that focus on the brain, psychological theories concern an indi- vidual’s feelings of cravings and pleasures that drugs provide. A major distinction among these theories is their emphases on different aspects of addiction.
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Opponent-Process Theory. This theory integrates psychological characteristics of drug motivation (Solomon & Corbit, 1974; Solomon, 1980). According to this theory, the initial positive hedonic process produced by a drug is opposed or counteracted by a negative he- donic process. The positive process is always the same and quickly subsides while the opponent process is slow to take effect and continues after the drug wears off. The oppo- nent process counteracts the disruptive effects of a drug reaction and is an attempt to restore homeostasis (balanced internal environment; see Chapter 5). Subjectively, an individual experiences the algebraic sum of these two processes. For example, inhaling nicotine from tobacco produces a positive hedonic feeling. This positive feeling, however, produces an opponent process to counteract the effects of nicotine. When the nicotine wears off, the posi- tive feeling ceases and the negative opponent feeling becomes dominant, which is felt as withdrawal (Solomon & Corbit, 1974). Repeated drug experiences strengthen the opponent process, while the strength of the initial positive process remains constant.
Incentive Sensitization Theory. Have you ever had a strong craving for some substance but then not enjoy it as much as expected? Is the degree of craving or wanting a drug linked with the amount of pleasure that is derived from consuming the drug? One line of thinking is that craving or wanting a drug is independent of the actual drug experience. According to incentive sensitization theory, craving or wanting results from the drug’s incentive value and not from its hedonic value (Robinson & Berridge, 2000, 2003). As a result of re- peated drug experiences, the addict’s brain becomes sensitized to drugs and associated drug stimuli, which affect wanting a drug more (incentive value) but not liking it more (hedonic value). Sensitization affects that part of the brain that leads to compulsively wanting and seeking drugs. Sensitization does not affect that part of the brain involved in liking drugs. In fact, the pleasure and euphoria from drug use actually decline slightly.
Conditioning Theories Craving is a major source of motivation for drug use. Thus, it is important to know what promotes craving and how it develops. Opponent-process theory implies that withdrawal and drug cravings eventually cease (Solomon & Corbit, 1974). However, this picture is in- complete. Although the young man in the example that opened the chapter was drug-free for over a year, his withdrawal symptoms returned. In the other example, the young woman’s craving for cocaine, dormant at the time, was suddenly activated on seeing the mir- ror. Thus, although an addict is not using drugs, craving in one form or another can be reinstated by the appropriate reminders.
Classical Conditioning. Classical conditioning combined with opponent-process the- ory can explain the return of withdrawal symptoms and druglike euphoria. In his experi- ments on conditioned reflexes, Pavlov (1927) reports how a dog’s reaction to morphine is conditionable. A dog’s natural reaction to morphine (unconditioned stimulus) is salivation, nausea, vomiting, and sleep (unconditioned responses). Preparation for the injection, such as seeing the removal of the syringe from its container, becomes the conditioned stimulus. After several days of repeated injections, the conditioned stimulus produces salivation and nausea (conditioned responses) before the actual injection. According to Solomon and Corbit (1974), during the process of repeated drug experiences, stimuli in the environment can become associated with a moderate degree of euphoria, as in the young woman’s case
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and also with withdrawal symptoms, as in the young man’s case. Consequently, addicted individuals become motivated for their drug of choice.
Conditioned Compensatory versus Conditioned Druglike Responses. How is it pos- sible that conditioned responses can be similar to withdrawal symptoms at one time yet be similar to drug-unconditioned responses at another? The answer lies in the nature of the conditioned response. In classical conditioning the conditioned response and the uncondi- tioned response are usually the same. However, there sometimes occurs what is called paradoxical conditioning in which the conditioned response is the opposite of the uncon- ditioned response (Black, 1965). These conditioned responses are called conditioned com- pensatory responses. Thus, two types of drug-conditioned responses are possible. One conditioned response is the opposite of a drug reaction, while the other one mimics a drug reaction. According to a conditioned compensatory response model, a conditioned drug response is in the opposite direction of the unconditioned drug response. The compensatory response offsets the effects of a drug (such as morphine) and returns the body to its normal state to maintain homeostasis. According to the conditioned druglike response model, conditioned drug stimuli are reminders that elicit conditioned responses similar to those evoked by the drug itself (Stewart, de Wit, & Eikelboom, 1984). In either model, the desire for drugs returns.
Events That Lead to Drug Relapse The motivation for drugs comes and goes. Even when an individual has quit using drugs for a time, she can relapse, which means going back to using drugs. A few major factors play a role in drug relapse: priming and the relief from stress.
Drug Priming with an Unconditioned Stimulus. “I’ll bet you can’t eat just one” is the slogan of a potato chip commercial. The slogan implies that the first bite increases your craving so strongly that further resistance is impossible. Priming means that a strong crav- ing for a drug can be reinstated with a single dose of alcohol, nicotine, cocaine, or heroin. Kirk and de Wit (2000) demonstrated priming with alcohol for social drinkers. During each experimental session, 22- to 25-year-old university undergraduates drank either a nonalco- holic beverage (placebo) or one containing a 0.2-, 0.4-, or 0.8-gram dose of alcohol mixed with tonic water and lime juice. Participants were not informed what the beverage contained. After drinking it, the participants rated their reactions for “feel” the effect, “like” the effect, feel “high,” and “want more” on a visual scale that ranged from 0 = Not at all or Dislike a lot to 100 = A lot or Very much. The results showed that all the ratings of the beverages increased above the placebo as the amount of alcohol increased. Participants felt the effects of the alcohol more, liked it more, experienced a greater high, and wanted more. All these effects are indicative of priming (Kirk & de Wit, 2000).
In addition, the effects of alcohol priming seem greater for heavy drinkers compared to light drinkers. Myrick and coresearchers (2004) compared individuals who averaged eight drinks per day (heavy drinkers) with those who averaged two drinks per day (light drinkers). Both a sip of alcohol and a picture of an alcoholic drink produced greater in- creases in craving among heavy drinkers than for the light drinkers.
Human addicts who are trying to quit their drug habit also run into the problem of priming. A single cigarette, drink of alcohol, or drug injection can reestablish craving and
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0 Beginning Ending
Without smoking stimuli With smoking stimuli
FIGURE 4.5 Priming Effects of Smoking Cues. Smokers traveled through a virtual neighbor- hood on a computer screen. When they encountered cues associated with smoking or cigarettes, their craving for a cigarette increased.
Source: Adapted from “Smoking Cues in a Virtual World Provoke Craving in Cigarette Smokers” by S. B. Baumann & M. A. Sayette, 2006, Psychology of Addictive Behaviors, 20, table 2, p. 487.
reestablish the drug habit. For example, following their participation in a stop smoking pro- gram, participants smoked their first cigarette 58 days later.They smoked their second cigarette only 9 days after that, with about half of the participants smoking their second cigarette within 24 hours after the first (Brandon et al., 1990). The first cigarette primed a craving for more cig- arettes. Thus, it appears that in trying to stop drinking, smoking, or using illegal drugs, one drink, smoke, or drug injection elicits the urge for another and another (Stewart, de Wit, & Eikelboom, 1984). In other words, the motivation for the person’s drug of choice returns.
Priming with a Conditioned Stimulus. Priming is also possible with conditioned stim- uli that are intimately associated with the drug-taking procedure. In this chapter’s opening vignette, the buildings and mirror on the coffee table are examples of conditioned stimuli associated with the use of heroin and cocaine. Drug-associated stimuli have been incorpo- rated into virtual reality technology, which refers to a realistic environment created on a computer screen. Individuals interact with the environment visually but also through sound via headphones and by means of a mouse, keyboard, or joystick. Baumann and Sayette (2006) primed the desire for cigarettes by embedding them in a virtual reality neighborhood scene. They had smokers navigate a virtual environment that began from an apartment building to the street, past a news stand, and then into a restaurant-bar filled with patrons. During the first run through the virtual environment, cigarette-stimuli were absent but those stimuli were present during the second run. On the second run, participants saw an open pack in the apartment, smokers on the street, cigarettes for sale at the news stand, and entered the bar filled with patrons who smoked. The participants rated their urge to smoke at the start and end of each run and at specific locations where cigarettes were either absent or present. The smoking urge was measured with a 100-point scale that ranged from 0 � absolutely no urge to 100 � the strongest urge I have ever experienced. The smoking- associated stimuli indeed increased the urge to smoke. Figure 4.5 shows that even when
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cigarette stimuli were absent, the urge to smoke increased from the beginning to the end of the virtual run. Many participants mentioned that in spite of the absence of cigarettes “there were many numerous unintentional and idiosyncratic cues that triggered their urges” (p. 486). Figure 4.5 also shows that the increase in the urge to smoke was greater when the virtual reality scenes were filled with the presence of cigarettes. The strongest smoking urges occurred in the presence of the bar scene that contained patrons who smoked. In a sim- ilar use of virtual reality, visits to a crack house evoked reactions to conditioned stimuli associated with cocaine use (Saladin et al., 2006). There was a tendency for most scenes in- volving cocaine to increase cravings for cocaine. Most effective were virtual reality scenes that portrayed dealing and using crack cocaine.
Stress and Drug Cravings. The motivation for drugs comes and goes partly as a result of priming. In addition, individuals can relapse as a result of stressful experiences. In these cases, drugs are consumed in order to alleviate stress. One line of evidence for this claim is based on comorbidity, which refers to the association between posttraumatic stress disorder (PTSD) and substance abuse (Brady et al., 2004). PTSD is the result of exposure to extremely trau- matic events, such as physical and sexual abuse or combat. Subsequent PTSD experiences in- volve physiological arousal, intrusive thoughts about the original trauma, and avoidance of stimuli associated with it (American Psychiatric Association, 2000). Comorbidity refers to the fact that people who suffer from PTSD are also more likely to be substance abusers than are members of the general population. According to the self-medication hypothesis, this asso- ciation is the result of PTSD sufferers attempting to reduce the negative feelings that arise when prior traumatic memories are relived (Brady et al., 2004). Longitudinal research shows that substance abuse occurs after PTSD has developed and not the reverse. Chilcoat and Breslau (1998) found that individuals who suffered from PTSD had a greater likelihood of becoming substance abusers than individuals who did not have PTSD. Furthermore, exposure to traumatic events that did not result in PTSD did not increase the likelihood of subsequent substance abuse. However, an alternative possibility suggested by Goeders (2004) is that the distress experienced during a PTSD episode sensitizes an individual to the effects of a drug. As a result the reinforcing value of the psychoactive drug increases.
Drug-Use Reinforcement What is experienced by an individual who has been subjected to priming or distress? Do drug-associated stimuli produce reactions that are opposite of the reaction evoked by the drug itself (Siegel, 2005) as in the conditioned compensatory-response model? In this case, the individual is motivated to reduce these feelings. Or do drug-associated stimuli elicit feel- ings similar to those evoked by the drug itself (Stewart, de Wit, & Eikelboom, 1984) as in the conditioned druglike response model? The addicted individual is motivated to intensify these feelings. There has been much debate whether drug use is motivated by escaping from drug lows or pursuing drug highs. We will examine these two possibilities next.
Positive Reinforcement. As described in the section on drugs of abuse, drugs make a person feel good, high, and euphoric, which are positive reinforcers for their continued use. A direct test of the positive feeling produced by caffeine and nicotine was performed by Garrett and Griffiths (2001). They gave different concentrations of caffeine, nicotine, or a
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placebo (nondrug) to their participants. Next, they asked the participants questions that per- tained to positive reinforcement, such as “How high are you?” and “Do you feel a rush?” The results showed that stronger doses of caffeine and nicotine were associated with reports of greater “highs” and “rushes.”
Negative Reinforcement. Drug abstinence produces withdrawal symptoms felt as negative affect, such as bodily distress, headaches, fatigue, dysphoria, anxiety, irritabil- ity, and sadness (APA, 2000; Baker et al., 2004). Drug-seeking behavior and use is neg- atively reinforced because it reduces withdrawal-generated negative affect according to the affective model of negative reinforcement (Baker et al., 2004). Several considera- tions support the model. First, negative affect characterizes a general withdrawal process along with drug-specific withdrawal symptoms. Specifically, alcohol withdrawal may in- volve tremors and sweating, cocaine withdrawal may involve fatigue and increased ap- petite, while nicotine withdrawal involves anxiety and insomnia (Jaffe et al., 2005). Accompanying these withdrawal symptoms is a craving for the very drug that produces the withdrawal. Thus, negative affect along with craving motivates seeking and using a variety of drugs. Second, withdrawal symptoms that are the basis for negative affect can occur early in drug use. A person need only use drugs for a short period of time in order to experience negative affect during withdrawal. For example, unpleasant withdrawal symptoms can occur after a first time use of an opiate like heroin (Harris & Gewirtz, 2005). Consequently, negative reinforcement as a motivator for drug use may accompany positive reinforcement early in the process of drug experimentation. Third, the intensity of negative affect increases with the duration of abstinence from drugs. As abstinence in- creases, there is greater relief from negative affect—that is, a greater amount of negative reinforcement.
Negative reinforcement implies escape, not avoidance behavior. The addict escapes or reduces negative affect that results from drug withdrawal. However, the anticipation of neg- ative affect can motivate drug use as a case of avoidance behavior. An addict uses a drug in order to prevent negative affect. One possibility is that an addicted individual is motivated to reduce the frequency with which withdrawal occurs (Herrnstein, 1969). Addicts may not be able to avoid withdrawal every time but they can reduce the frequency of it happening. Furthermore, the affective model of negative reinforcement states that the process of addic- tion involves many repetitions of the following cycle: drug levels drop in the body, negative affect follows, and drug use reduces negative affect. An addict becomes sensitive to the drop in drug levels and experiences it as bodily cues. These cues signify the initial emergence of negative withdrawal into conscious awareness. Consequently, these bodily cues set the oc- casion for drug use in order to avoid aversive withdrawal symptoms (Baker et al., 2004).
Cognition and Addiction The descriptions of drug addiction given thus far have been mostly mechanistic, with no mention of the role of cognitive processes. The addicted individual was described as re- acting to stressful events and to drug-associated stimuli that evoke craving or withdrawal symptoms. The person was not seen as making an active attempt to approach or avoid these situations. Furthermore, mechanistic models minimize the possibility of a person willfully quitting. Therefore, trying to reduce or eliminate drug dependence would be difficult to accomplish. Bandura’s (2006) agentic theory (see Chapter 1) may be a way out of this
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difficulty. According to this theory, humans can intentionally create their circumstances. Thus, an individual has control over whether she wants to continue exposing herself to drugs.
A feature of the interplay between cognition and addiction is the motivation for change (DiClemente, 1999; DiClemente et al., 2004). This motivational factor represents various stages of change from a person willfully contemplating change, to preparing for it, acting on it, and maintaining that change. For instance, a drug abuser begins by contem- plating a change in his drug use by considering the pluses and minuses of such an action. Next, an individual might commit to change. As part of that commitment, for example, he might say, “I am planning to reduce my cigarette consumption by 10% beginning next month.” Then when the time arrives, he initiates the plan and maintains his reduced ciga- rette intake, perhaps quitting eventually. His plan might be to start the day with a certain self-imposed cigarette allotment. If those are smoked prior to the end of the day, he will not seek more cigarettes. DiClemente (1999; DiClemente et al., 2004) points out that the suc- cess of motivation for change and eventually quitting depends on the incentives that are em- ployed at each stage. Incentives imposed from outside are less effective than self-imposed ones. For example, court-ordered drug treatment is less effective than if a person decides for himself to seek treatment. Personal reasons for quitting are much more effective.
Section Recap The motivation for drug use is based on attaining pleasure (positive reinforcement) or reduc- ing withdrawal symptoms (negative reinforcement). These reinforcing events emerge from the activation of neurons at critical locations in the brain. The brain is composed of billions of neurons, which are cells that send and receive information by way of electrical nerve im- pulses. Neurotransmitters are chemicals at the end of sending neurons that diffuse across a synapse or gap and stimulate receiving neurons, which then send out their own nerve im- pulses. Dopamine is the neurotransmitter that activates neurons in the mesolimbic dopamine system from which feelings of pleasure and euphoria emerge into consciousness. The eu- phoric effects produced in the mesolimbic dopamine system are powerful, since rats will work long and hard to have these areas electrically stimulated. Psychoactive drugs produce their pleasurable effects when they reach the mesolimbic dopamine system. There the drugs in- crease the amount of dopamine by either blocking the reuptake or promoting the release. More dopamine is associated with greater pleasure. The natural function of dopamine is to provide pleasure for survival activities, such as eating, drinking, and sex. Antagonists are substances capable of blocking the pleasurable effects of psychoactive drugs. As a consequence, the mo- tivation for cocaine, heroin, or alcohol can be reduced with the use of appropriate antagonists.
There are a number of psychological theories that stress various aspects of priming, craving, and euphoria. According to opponent-process theory, the initial pleasurable reac- tion to a drug is held in check by an opponent process or drug-opposite effect characterized by dysphoria and withdrawal. The strengthening of the opponent process is responsible for drug tolerance and withdrawal. Incentive sensitization theory emphasizes that individuals are motivated by a drug’s incentive value (anticipated pleasure) and not by its hedonic value (actual pleasure). For the conditioned compensatory response model, stimuli associated with drugs evoke conditioned responses that are the opposite of drug-unconditioned responses. The conditioned druglike response model, however, states that the conditioned
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drug response is similar to the unconditioned drug response. Either model accounts for priming, which refers to the development of cravings whether by being exposed to the drug itself or to stimuli associated with the drug. Craving increases the likelihood of drug use or relapse. Craving and drug use also occur in order to relieve distress, depression, anxiety, or boredom. Thus, there is the tendency for comorbidity, which is the joint occurrence of dis- tress from PTSD, for example, and drug use. According to the self-medication hypothesis, individuals with PTSD take psychoactive drugs in order to reduce negative feelings that are evoked by traumatic memories.
Positive reinforcement effects of drug use are the pleasurable euphoric effects. In con- trast, negative reinforcement refers to the alleviation of unpleasant withdrawal symptoms. According to the affective model of negative reinforcement, repeated drug use allows ad- dicts to be sensitive to the symptoms that predict withdrawal. As a consequence, drug use occurs in order to prevent the anticipated negative effect. Based on agentic theory a person can effect a motivation for change. This change represents the stages from willfully plan- ning to reducing drug use.
Behavioral Addictions This is the case of a 20-year-old woman who had been running since age 10 and was now in leg casts because she severely sprained both ankles:
I would sit all day and let my thoughts build up—I would go out at night to drink, I became so frustrated and confused I didn’t realize what was important anymore. I ended up sick in bed for 21⁄2 months because of my involvement in drinking and drugs because of my inability to run. (Morgan, 1979, p. 63)
This individual is addicted to running rather than drugs. She craves running, suffers withdrawal when unable to run, and runs despite adverse consequences.
The purpose of this section is to examine whether principles of drug addiction can ac- count for exercise addiction and gambling addiction.
Exercise Addiction and Drug Addiction Drugs are considered negative addictions because their use has long-term negative conse- quences. Positive addiction (Glasser, 1976), however, refers to compulsive behaviors that re- sult in positive health consequences. This is a term applied mainly to runners and strenuous exercisers. Like drug use, running or strenuous exercise produces a runner’s high or exercise high. This refers to a state of euphoria involving exhilaration, mood improvement, and even- tually relaxation. People can become addicted to this feeling, and the effect of compulsive run- ning or exercise can be equated with drug addiction.
Reinforcers. The rewards for running are the consequences that maintain this activity. Summers and associates (1983) asked marathoners who had been running about two years why they ran. Their reasons fell into three categories: physical health (being physically fit, losing weight), psychological health (feeling relaxed, enjoying life), and goal achievement (meeting a challenge, training for a marathon). Some reasons were classified as negative re- inforcers, such as relieving depression and tension. The most rewarding consequence, how- ever, was runner’s high, which occurred in the latter part of or when finished with a run.
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Some runners reported experiencing “spin out,” which is a detached dreamy state of mind (Carmack & Martens, 1979; Summers et al., 1982). The length of a run seemed to correlate with the feelings characteristic of spin out. For example, runners who ran 40 minutes or more experienced spin out with a greater frequency than those who ran a shorter length of time. Other exercisers report “feeling high” or feeling like being “on speed” following periods of intense training (Griffiths, 1997).
The relationship between exercise intensity and “feeling high” has been verified in the laboratory. For instance, Blanchard and coresearchers (2002) had female university stu- dents exercise for 15 minutes on a stationary bicycle. Students felt significantly more pos- itively engaged (happy, enthusiastic, upbeat) and revitalized as a result. These positive feelings seemed to increase with exercise intensity. Cox and coresearchers (2006) had women run on a treadmill for 33 minutes at either 60% (low intensity) or at 80% (high in- tensity) of their maximum aerobic capacity. Post-exercise, the participants rated their pos- itive well-being on a seven-point scale. The ratings showed that as exercise intensity increased, positive well-being increased compared to a non-exercise control condition. In addition, positive well-being remained significantly high even 80 minutes post-exercise.
Exercise Tolerance. While drug tolerance refers to the diminishing effects of a constant drug dose, running tolerance means a decline in the euphoric effects that result from run- ning. One cause of this decline is that a person becomes physically conditioned so running becomes less stressful. To experience the same level of runner’s high, a runner has to in- crease the mileage, frequency, or pace of running (Morgan, 1979). The upper limit of this increase, however, is the body’s ability to tolerate such stress. When mileage increases, run- ning injuries develop (e.g., hip pain, knee and back injuries, stress fractures, Achilles tendon, and foot problems). For example, a woman who appeared addicted to jiujitsu exhibited exercise tolerance. She started training once a week, but after five years she now exercises every day of the week for longer and longer periods of time (i.e., six hours) (Griffiths, 1997).
The concept of tolerance points out one fundamental difference between exercise addiction and drug or alcohol addiction. Exercise addiction requires the individual to make considerable physical and mental effort in contrast to what is required for drug or alcohol addiction (Cockerill & Riddington, 1996). In the case of exercise, an individual must become physically fit in order to experience euphoria, whereas drug or alcohol ad- diction requires less effort for the individual to experience any positive effects. Further- more, when individuals are forced to withdraw from exercise due to injuries, they are not likely to quickly resume their exercise addiction. It will be necessary for them to retrain to achieve a level of fitness necessary to again experience any euphoric effects (Cockerill & Riddington, 1996).
Withdrawal. For individuals who chronically exercise, exercise deprivation results in symptoms akin to physiological and psychological withdrawal. These symptoms appear to reflect a dependence on exercise (Adams & Kirby, 2002). In the case of runners, Morgan (1979) notes that when they cannot run, addicted runners feel depressed, anxious, and irri- table and also suffer from muscle tension, decreased appetite, and constipation.
In an actual exercise-withdrawal experiment performed by Mondin and coresearchers (1996), individuals who exercised (running, jogging, or swimming) six to seven days per week were paid $50 not to exercise on Tuesday, Wednesday, and Thursday. Participants filledIS
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out various psychological scales each day of the week in order to measure various indica- tors of their moods before, during, and after their exercise deprivation. The results showed that state of anxiety, tension, and depression increased from Monday to Wednesday and then decreased. These three indicators of the negative effects of exercise deprivation were great- est on the second day of deprivation, which indicates that withdrawal symptoms begin to occur after 48 hours. The decline in anxiety, tension, and depression on Thursday may indicate the participants’ awareness that they could resume exercising the next day (Mondin et al., 1996).
In another exercise-withdrawal experiment, one group of regular male runners was paid not to run for two weeks. A control group of regular runners continued their usual run- ning routine (Morris et al., 1990). Both groups filled out questionnaires measuring anxiety and depression before and during the enforced abstinence interval and after running re- sumed. The two groups did not differ in anxiety and depression before the abstinence in- terval and after running resumed. The effect of running deprivation became apparent during the second week, when the deprived runners reported greater anxiety and depression. In ad- dition, the deprived runners complained of more social dysfunction and somatic symptoms that developed during their first week of deprivation (Morris et al., 1990).
Addiction. Running is considered addicting if a person craves a runner’s high, organizes his life around opportunities to run, and runs as much as possible in spite of negative con- sequences. Runners report being addicted to running (Summers et al., 1983). Using case studies, Morgan (1979) illustrated the addictive nature of running by observing that ad- dicted runners feel compelled to exercise daily. When unable to do so, they feel withdrawal symptoms, including anxiety, irritability, and depression. The individual insists on running despite deteriorating interpersonal relationships in social settings, the workplace, or even at home. For example, spouses may complain about being neglected because their mates spend so much time running. In addition, the addicted individual continues running in spite of injuries. Some runners only stop after the pain from their injuries becomes unbearable.
There are several factors that exhibit a person’s dependence on or addiction to exer- cise in general. Ogden and associates (1997) uncovered eight factors with the development of their Exercise Dependence Questionnaire. Three of the factors involve interference, withdrawal, and insight. The interference factor reflects the extent exercise interferes with one’s family, social, and work life. For instance, a person would report missing work in order to exercise. The withdrawal factor describes the negative feelings that are experienced when a person misses exercising for some reason. For example, a person would report being agitated or irritable when an exercise session is missed or hating being unable to exercise. The insight factor indicates that people are aware that their dependence on exercise is caus- ing a problem. The person would report feeling guilty about the amount he exercises and would realize it is ruining his life but feel unable to cut back. Ogden and associates (1997) found that these factors became more severe with either an increase in the number of years of exercise or an increase in the number of weekly hours of exercise.
Another scale, named the Exercise Dependence Scale, contains 21 questions that measure additional components of exercise addiction (Hausenblas & Downs, 2002). For in- stance, an individual’s continuance and lack of control are probed by the extent he contin- ues to exercise despite physical problems and the extent he feels unable to reduce his
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frequency. A question relevant for exercise tolerance asks the extent a person feels a lack of benefit from his current level of exercise.
➣ The Exercise Dependence Scale is available at http://www.personal.psu.edu/dsd11/EDS/ index.html
Endorphins and Exercise-Induced Euphoria As documented in the section on reinforcers, exercise induces positive feelings. Are these feelings of an exercise high related to the neurotransmitters associated with the brain’s pleasure centers? One hypothesis revolves around a set of opioid neurotransmitters of which endorphins are a special case. The term endorphin refers to internal morphine (endo for endogenous or internal and phin for morphine). Endorphins are primarily located in the pain pathways and are responsible for reducing the negative effects of pain stimuli and stressors. Perhaps that is why endorphins are implicated in a runner’s high because running is a stressful activity. The endorphin–exercise high connection holds that endorphins released during strenuous exercise act on pleasure neurons and those that are linked to pleasure neurons (Adams & Kirby, 2002). One possibility is that running-induced endor- phins eventually affect the mesolimbic dopamine system where feelings of pleasure occur (Nestler, 2005).
According to the endorphin–exercise high connection, exercise-induced mood changes should correlate with endorphin changes. Harte and associates (1995) examined positive and negative mood changes and β-endorphin-level changes in elite runners before and after a hard 15-kilometer (9.3 mile) run. Their findings show that following the hard run, positive mood increased and negative mood decreased. The researchers also found that β-endorphins in the runners’ blood also increased over the course of the run. Thus, β-endorphin-level increases were accompanied by mood changes resembling runner’s high. Wildmann and associates (1986) also showed that a feeling of pleasantness correlated with blood β-endorphin values of male runners who had completed two 10-kilometer (6.2 mile) runs. Higher levels of β-endorphin circulating in a runner’s blood accompanied greater feel- ings of pleasure. However, the fact that endorphin changes correlated with mood changes in these studies does not mean that endorphin changes caused the mood changes. A third variable besides endorphins may be responsible for runner’s high.
Gambling Addiction Gambling is another example of a behavioral addiction that some people find difficult to con- trol. In fact, the first step in a 12-step recovery program for addicted gamblers requires indi- viduals to admit that they are powerless over gambling (www.gamblersanonymous.org). Addicted gamblers can become so involved with gambling that their behavior resembles drug addiction. Addicted gamblers constantly seek out opportunities to gamble and are not sensi- tive to any negative financial and social consequences. When gambling reaches the level of an addiction, negative behaviors ensue, which are detrimental to a person’s well-being.
The incidence of gambling addicts in society has grown as a result of increased gam- bling opportunities over the last two decades. Whereas previously illegal, now most states allow casinos, lotteries, and scratch-off cards. Gambling has also attained more social ac- ceptance, especially when states use their gambling profits for the greater social good, such
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0 10 20 30 40 50 60 70
Maxed-out credit cards
Lying to friends, family
No more savings, retirement
Borrow money for food, bills
File for bankruptcy
Lost home, car, pawn
Difficulties at work
FIGURE 4.6 Consequences of Pathological Gambling. These negative behaviors attest to the addictive nature of gambling. The most frequent consequence was a maxed-out credit card, and the least frequent consequences were difficulties at work.
Source: Adapted from “Demographic and Clinical Features of 131 Adult Pathological Gamblers” by J. E. Grant and S. W. Kim, 2001, Journal of Clinical Psychiatry, 62, pp. 959–960.
as education and counseling for gambling addicts. Shaffer and colleagues (1999) examined estimates of the prevalence of individuals with gambling problems. Prior to 1993, an esti- mated 0.84% of surveyed adults reported experiencing pathological gambling problems during the preceding year. This estimate rose significantly to 1.29% after 1993. Estimates of less severe gambling problems also rose significantly during this time.
Characteristics of Addicted Gamblers. One strategy for determining the powerful motivational effects of gambling is to uncover characteristics of addicted gamblers and the psychological costs incurred. With these goals in mind, Grant and Kim (2001) interviewed 131 individuals who had been diagnosed as pathological gamblers. These individuals played slot machines, cards, blackjack, and the lottery for an average of 16 hours per week and had lost an average of 45% of their annual income during the preceding 12 months. Interview results in Figure 4.6 attest to the addictive nature of gambling by showing the percentage of gamblers who experienced various negative consequences. Notice that nearly two-thirds had maxed out their credit cards. After losing nearly all of their assets, nearly one-fourth of the addicted gamblers engaged in at least one form of illegal activity, such as writing bad checks, embezzling money at work, and committing tax fraud. Negative social conse- quences involved lying to friends and family members and experiencing marriage or work difficulties.
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Gambling Priming. Gambling urges and behavior can be primed much like drug cravings can be. Environmental stimuli that evoke gambling urges include television and billboard ad- vertisements, thoughts of winning, receiving payment, hearing conversations about gambling, and the sight and sounds of a casino (Grant & Kim, 2001). In addition to priming, gambling- associated stimuli increase a compulsive gambler’s level of arousal. This is a pleasant feeling that helps reinforce gambling behavior (Sharpe, 2002). Furthermore, just as stressful events can produce drug cravings, so can they produce urges to gamble. For example, boredom, lone- liness, depression, stress, and anxiety all contribute to gambling urges (Grant & Kim, 2001).
Dopamine and Gambling. Like drugs and running, the pleasure derived from gambling may also depend on the extent that this activity activates the mesolimbic dopamine system (Blum et al., 2000; Sharpe, 2002). However, not much is known about how gambling re- lates to dopamine. Gambling addiction does not occur in isolation but is often associated with other drug activities. For example, DeCaria and colleagues (1996) cite studies that compulsive gamblers are also likely to have problems with alcohol and illicit drugs. In their survey of 131 pathological gamblers, Grant and Kim (2001) found that 27% also suffered from alcohol dependence or abuse and 8.4% suffered from other forms of drug dependence or abuse. This association between pathological gambling and other forms of licit and illicit drug use warrants the search for a common brain substrate.
The drug naltrexone has been used effectively to help curb a person’s appetite for heroin, cocaine, and alcohol (Goldstein, 2001; O’Brien, 2005). Naltrexone has also been employed to curb compulsive gambling. Kim and coresearchers (2001) tested the hypothe- sis that pathological gambling is triggered by its potential reward, which involves the ac- tions of dopamine. Therefore, if naltrexone inhibits the release of dopamine, the impulse to gamble should decrease. The researchers gave one group of pathological gamblers a daily pill of naltrexone for 11 weeks, while another group of pathological gamblers received a placebo. Weekly evaluations showed that naltrexone reduced the symptoms of pathological gambling more than the placebo did. Naltrexone reduced the urge to gamble and reduced the subjective pleasure that gambling provided. The results of this study and the association of gambling with alcohol and other drugs support the idea that the mesolimbic dopamine system is involved in gambling addiction.
➣ The home page of Gamblers Anonymous is at http://www.gamblersanonymous.org. The home page for Alcoholics Anonymous is at http://www.aa.org
Section Recap The use of psychoactive drugs is a negative addiction, while repeated strenuous exercise is a positive addiction because of the supposed health benefits. However, extensive exercise also has characteristics of negative addiction. Exercise addiction has several similarities with drug addiction. Humans can develop a tolerance for exercise, show withdrawal symp- toms when unable to exercise, and behave as if they are addicted. There are exercise- dependence scales that measure the extent of a person’s addiction. Strenuous exercise provides several positive reinforcers, with the major one being the exercise high, which in- volves feelings of euphoria, exhilaration, positive mood, and relaxation. According to the endorphin–exercise high connection, strenuous exercise releases endorphins, which bind with neurons that are eventually responsible for the feelings of euphoria and exhilaration.
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Gambling is another addictive behavior that is pleasurable because it activates the mesolim- bic dopamine system. This claim is based on the association between gambling behavior and drug or alcohol use. It is also based on the curbing effects that naltrexone has on gambling urges and pleasures.
A C T I V I T I E S
1. Consider conducting the following experiment on yourself in order to understand craving:
a. Hide a piece of your favorite chocolate from view, and while it is hidden think about eating it.
b. Next, place the chocolate in front of you and stare at it.
c. Then unwrap it and deeply inhale the chocolate’s aroma for a minute or two.
d. Finally, nibble at the chocolate and try to maximize the flavor sensation that you feel.
Under each condition a through d, rate your de- sire or craving for the piece of chocolate using a nine-point scale:
No desire at all � 0 Very strong desire � 9
Did the intensity of your craving increase through steps a through d? People vary widely in their ratings, especially in steps c and d. Why do you think that happens? What does it mean to be a “chocaholic”? What factors in- fluence one person to become a chocaholic and another to be indifferent about chocolate?
2. Do you engage in any strenuous exercise, such as biking, running, swimming, or race-pace walking? If so, do you experience any feel- ings resembling an exercise high? Is this feel- ing part of what motivates you to continue exercising?