TOBACCO USE AND THE DEVELOPMENT OF DEPENDENCE

Although not true for every tobacco user, the vast majority of users, particularly cigarette smokers, will develop a dependency relationship with the nicotine contained in tobacco.  This state of dependence causes users to consume greater quantities of nicotine over extended periods of time, further endangering their health.

Dependence can imply both a physical and psychological relationship.  Particularly with cigarettes, physical dependence or addiction, with its associated tolerance, withdrawal, and titration, is strongly developed by 40 percent of all smokers.  The development of addiction reflects a strong genetic predisposition to physical dependence.  Most of the remaining population of smokers will experience lesser degrees of physical dependence.  Psychological dependence or habituation, with its accompanying psychological components of compulsion and indulgence, is almost universally seen.

Compulsion is a strong emotional desire to continue tobacco use despite restrictions on smoking and the awareness of health risks.  Very likely, users are “compelled” to engage in continual tobacco use in fear of the unpleasant physical, emotional, and social effects that result from discontinuing use.  In comparison to compulsion, indulgence is seen as “rewarding” oneself for aligning with a particular behavior pattern  - in this case, smoking.  Indulgence is made possible by the existence of various reward system built around the use of tobacco, including a perceived image, group affiliation, and even appetite suppression intended to foster weight control.

Much to the benefit of tobacco industry, dependence on tobacco is easily established.  Many experts believe that physical dependence on tobacco is far more easily established than is physical dependence on alcohol, cocaine (other than crack), or heroin.  Of all people who experiment with cigarettes, 85% develop various aspects of a dependence relationship.

A small percentage of smokers, known as “chippers,” can on occasion without becoming dependent.  Most likely, chippers respond differently to environment cues than do more dependent smokers, thus smoking less frequently.  They may be truly “social smokers” in that they smoke with only a few selected friends or in a very limited number of places.  Unfortunately, many inexperienced smokers feel that they too are only social smokers; however, a few months, or even a few days, of this type of occasional smoking could be a transitional period into a dependence pattern of tobacco use.

Sandwiched between regular smokers and chippers is a newly emerging group of smokers – part-time smokers.  Today these smokers constitute about 23% of all smokers.  The practice most likely reflects the reality of the high cost of cigarettes and restrictions in the workplace.  The health effects of this form of smoking appear to be the same as for regular smokers.

Theories of Nicotine Addiction

The establishment and maintenance of physical dependence or addiction is less than fully understood.  Most experts, however, believe that for a specific individual, addiction has a multifaceted etiology, or cause, with increasing attention being directed toward a genetic basis for addiction.  Accordingly, several theories have been proposed to explain the development of dependence.  Readers are reminded that many of these theories are technically sophisticated and only a most basic description can be provided in a personal health textbook.

Genetic Influences

Although the specific genetic pathways that influence both the initiation and maintenance of smoking (or other forms of tobacco use) are less than fully understood, a role for genetic influence is evident.  Applying new statistical techniques to earlier studies of smoking patterns in families and between identical twins, it is now believed that initiation and maintenance of initial smoking is 60% driven by genetic influences.  Of course, the smoking of the first few cigarettes is a choice made by beginning smokers.  The remaining influence needed for initiation and maintenance of initial smoking is 20% environmental and 20% the unique needs of individuals.

Once the brief period of initial exposure is passed, the role of genetic influences may be even more powerful – providing 70% of the stimulus required over decades of smoking.  Environmental and personality factors subside accordingly.

Bolus Theory

In the bolus theory of nicotine addiction, one of the oldest and most general theories of addiction, each inhalation of smoke release into the blood a concentrated quantity of nicotine (a ball or bolus) that reaches the brain and results in a period of neurohormonal excitement.  The smoker perceives this period of stimulation as pleasurable but, unfortunately, short lived.  Accordingly, the smoker attempts to reestablish this pleasurable feeling by again inhaling and sending another serve to condition the novice smoker, resulting in a lifelong pattern of cigarette dependence.  The level needed for arousal is different for each individual smoker, depending on the length of addiction, the level of tolerance, genetic predisposition, and environmental and personal stimuli.

Recognition of two types of smokers emerges from an understanding of the bolus theory of smoking.  Peak smokers are those smokers who become who become dependent on the arousal of pleasure centers in the brain that are stimulated by the rapid increase of nicotine within the CNS.  In contrast, the trough maintenance smokers maintain an even consistently higher level of nicotine titration in order to avoid the negative consequences of withdrawal.  These feelings are experienced as unpleasant, and thus to be avoided.

Adrenocorticotropic Hormone (ACTH) Theory

Yet another theory of dependence suggest that nicotine stimulates the release of adrenocorticotropic hormone (ACTH) from the anterior pituitary, or “master gland” of the endocrine system causing the release of beta endorphins (naturally occurring opiate-like chemicals) that produce mild feelings of euphoria.  Perhaps this stresslike response mechanism involving ACTH accounts for the increased energy expenditure seen in smokers and thus their tendency to maintain a lower body weight.  Others, however, have questioned the ability of nicotine to stimulate endorphin release.

When these psychological responses are viewed collectively, nicotine may be seen as biochemically influencing brain activity by enhancing the extent and strength of various forms of “communication” between different brain areas and even glands of the endocrine system.  If this is the case, it is apparent why, once addicted, the functioning of the smoker’s control system is much altered in comparison with that of nonsmokers.

Self-Medication Theory

Another explanation of addiction to smoking, called self-medication, suggest that nicotine, through the effects of mood-enhacing dopamine, may allow smokers to “treat” feelings of tiredness, lack of motivation, or even depression.  In other words, a smoke lifts the spirit the spirits, if only briefly.  Eventually, however, smokers become dependent on tobacco as a “medication” to make themselves feel better.  Thus, because tobacco is a legal drug that is readily available, it becomes preferred to prescription medications and illegal drugs, such as cocaine and the stimulants, that elevate mood.

Regardless of the mechanism involved, as tolerance to nicotine develops, smoking behavior is adjusted to either maintain arousal or prevent the occurrence of withdrawal symptoms.  At some point, however, the desire for constant arousal is probably superseded by the smoker’s desire not to experience withdrawal.

The importance of nicotine as the primary factor in establishing dependence on tobacco is supported by research that demonstrates that smokers will not select a nontobacco cigarette if a tobacco cigarette is available.  Even tobacco cigarettes with a very low level of nicotine seem to be unacceptable to most smokers, as do cigarettes with very low nicotine but with high tar content.  Interestingly, users of low-nicotine cigarettes tend to inhale more frequently and deeply to obtain as much nicotine as possible.

Even more impressive (and alarming) regarding nicotine’s dependency-producing power is seen in conjuction with the small amount of time needed to become dependent.  Using the HONC instruments, it is now established that beginning smokers (recall that most smokers begin during adolescence) become dependent on cigarettes within 3 weeks to 3 months of smoking on as little as two cigarettes per day.  Males are more likely to be a bit more resistant to dependency, taking a month or 2, while females can become dependent in a matter of a very few days of initial experimentation.  

Acute effects of Nicotine on Nervous System Function

In comparison with the more chronic effects of nicotine on the central nervous system (CNS) that may eventually result in physical dependence or addiction, nicotine also produces changes of short duration.  In the CNS, nicotine activates receptors within the nucleus accumbens (a reward center) and the locus caeruleus (a cortical activating center) of the brain.  Stimulation of the brain is seen by changes in electroencephalogram (EEG) patterns, reflecting an increase in the frequency of electrical activity.  This is part of a general arousal pattern signaled by the release of the neurotransmitters norepinephrine, dopamine, acetylcholine, and serotonin.  Heavy use of tobacco products, result in high levels of nicotine in the bloodstream, eventually produces a blocking effect as more and more receptor sites for these neurotransmitters are filled.  The result is a generalized depression of the CNS.

The level of plasma nicotine associated with normal levels of heavy smoking (one to two packs per day) would not likely produce the depressive effect just described.  However, in chain smokers (four to eight packs per day), plasma nicotine levels would be sufficient to have a depressive influence on nervous system function. In fact, it has been suggested that chain smoking is driven by fruitless effort to counter the depressive influence of chronically excessively high levels of nicotine.

In carefully controlled studies involving both animals and humans, nicotine increased the ability of subjects to concentrate on a task. It must be noted, however, that the duration of this improvement was limited.  Most would agree that this brief is not enough to justify the health risks associated with chronic tobacco use.

Non-Nervous System Acute Effects of Nicotine

Outside the CNS, nicotine effects the transmission of nerve signals at the point where nerves innervate muscle tissue (called the neuromuscular junction) by mimicking the action of the neurotransmitter acetylcholine.  Nicotine occupies receptor sites at the junction and prevents the transmission of nerve impulses from nerve cell to muscle cell.

Nicotine also causes the release of epinephrine from the adrenal medulla, which results in an increase in respiration rate, heart rate,, blood pressure, and coronary blood flow.  These changes are accompanied by the constriction of the blood vessels beneath the skin, a reduction in the motility in the bowel, loss of appetite, and changes in sleep patterns.

Although a lethal dose of nicotine could be obtained through the ingestion of a nicotine-containing insecticide, to “smoke oneself to death” in a single intense period of cigarette use would be highly improbable.  In humans, 40 to 60 mg (.06- .09 mg/kg) is a lethal dose.  A typical cigarette supplies .05 to 2.5 mg of nicotine, and that nicotine is relatively quickly broken down for removal from the body.

Psychological Factors Related to Dependence

You will recall that psychological aspect of dependence (habituation) exists and is important in maintaining the smoker’s need for nicotine.  Both research and general observation support many of the powerful influence this aspect of dependence possesses, especially for beginning smokers, prior to the onset of physical addiction.  Consequently, in the remainder of this section, we will explore factors that may contribute to the development of this aspect of dependence.

Modelling

Because tobacco use is a learned behavior, it is reasonable to accept that modelling acts as a stimulus to experimental smoking.  Modelling suggest that susceptible people smoke to emulate, or model their behavior after, smokers whom they admire or with whom they share other types of social or emotional bonds.  Particularly for young adolescents, smoking behavior correlates with the smoking behavior of slightly older peers and very young adults (ages 18 to 22), older siblings, and, most importantly, parents.

Negative parental influences on cigarette smoking by their own children include their own smoking in combination with their failure to clearly state their disapproval of smoking by children.  Further, for parents who smoke, it is important that they cease smoking before their children turn 8 years of age if they wish to maximize an anti-smoking message.

Modelling is particularly evident when smoking is a central factor in peer group formation and peer group association and can lead to a shared behavioral pattern that differentiates the group from others and from adults.  Further, when risk-taking behavior and disregard for authority are common to the group, smoking becomes the behavioral pattern that most consistently identifies who lack self-directedness or the ability to resist peer pressure, initial membership in a tobacco-using peer group may become inescapable.  The ability to counter peer pressure is a salient component of successful anti-smoking programs for use with older children and younger adolescents.

In addition, when adolescent have lower levels of self-esteem and are searching for an avenue to improve self-image, a role model who smokes is often seen as tough, sociable, and sexually attractive.  These three traits have been played up by tobacco industry in their carefully crafted advertisements.  In fact, teens from any background may see the very young and attractive models used in tobacco (and beer) advertisements as being more peer-like in age than they really are.  FCC regulations require that models for both products be 21 years of age or older, regardless of how youthful they might (and the advertisers hope they do) appear to older children and young adolescents.

Manipulation

In addition to modelling as a psychosocial link with tobacco use, cigarette use may meet the beginning smoker’s need to manipulate something and at the same time provide the manipulative “tool” necessary to offset the boredom, feelings of depression, or social immaturity.  Clearly the availability of affordable smoking paraphernalia provides smokers with ways to reward themselves.  A new cigarette lighter, a status brand of tobacco, or a beach towel with a cigarette’s logo are all reinforcements to some smokers.  Fortunately, the latter will become increasingly harder to find as logos can no longer be placed on items such as beach towels.  For others, the ability to take out a cigarette or fill a pipe adds a measure of structure and control to situations in which they might otherwise feel somewhat ill at ease.  The cigarette becomes a readily available and dependable “friend” to turn to with the use of its products.  To these users and potential users, the self-reward of power, liberation, affluence, sophistication, or adult status is achieved by using the products that they are told are associated with these desired states.  Thus the self-rewarding use of tobacco products becomes a means of achievement.

With this multiplicity of forces at work, it is impossible to understand why so many who experiment with tobacco use find that they quickly become dependent on tobacco.  Human needs, both physiological and psychosocial, are many and complex.  Tobacco use meets the needs on a short-term basis, whereas dependence, once established, replaces these needs with a different, more immediate set of needs.

Despite the satisfaction of the dependency that continued smoking brings, approximately 80% of adult smokers have, on at least one occasion, expressed a desire to quit, and the majority of these have actually attempted to become nonsmokers.  Today, with the over-the-counter availability of transdermal nicotine patches, nicotine containing gum, prescription medications such as antidepressants, and nicotine inhalers, the number of smokers making concerted and repeated attempts to stop smoking is up considerably over that seen in the past.  It therefore seems apparent that tobacco use is a source of dissonance.  This dissonance stems from the need to deal emotionally with a behavior that is both highly enjoyable and highly dangerous but known to be difficult to stop.  The degree to which this dissonance exists probably varies from user to user.

Preventing Teen Smoking

Even before the 1997 release of tobacco industry documents confirming the targeting of young adolescents, the federal government stated its intention to curb these cigarette advertisements.  In August 1995 the FDA described the specific actions that it hoped it would be given authority to implement.  Collectively, the restrictions described in the following list were intended to discourage cigarette smoking among American’s teens, resulting in 50% fewer adolescents beginning smoking in the year 2002 than in 1995.

1. Limit tobacco advertising in publications that appeal to teens and restrict billboards with tobacco-related content to no closer than 1,000 feet of schools and playgrounds.  (A August 1995 study in California found that stores near schools displayed significantly more tobacco-related advertisements than those far from schools.)
2. Restrict the use of logo and other tobacco-related images on nontobacco-related products, such as towels, T-shirts, and caps.
3. Bar certain sources of access to tobacco products, such as mail order sales, the distribution of free samples, and vending machines.
4. Halt sponsorship of high-visibility events, such as auto racing and athletic contents in which brand names appear on highly televised surfaces, including hoods, fenders, uniforms, and arena sign boards.  (It is estimated that the Marlboro logo is seen 5,933 times during the course of a 90-minute televised Winston Cup auto race).)
5. Require merchants to obtain proof of age when selling tobacco products to adolescents.  (This particular component of the initial plan became law in 1997.  Merchants are required to validate the age of people whom they suspect to be younger than 27 years of age before selling cigarettes to those 18 years of age and older.  If found in violation, both the salesperson and the store owner will be fined $500.)

By mid-1998 the federal government’s desire to reduce youth smoking through implementation of the steps just described was mired in a larger package of tobacco-related policies being debated in Congress.  This undertaking was relating to the class action suit filed by all 50 (46 as a single large class and 4 as a smaller class) states against the tobacco industry in an attempt to recoup Medicaid expenditures for treating tobacco-related illnesses.  As Congress attempted to construct a settlement that would be acceptable to all parties, the impasse fragmented attempts to reduce youth smoking.  Unfortunately, this outcome diluted some restrictions on tobacco advertisements, as well as the FDA’S ability to reduce smoking by defining cigarettes as drug delivery systems.  In fact, in 2000 the United States Supreme Court ruled that the FDA lacked the regulatory authority to bring tobacco products under its control, unless Congress was willing to rescind laws that currently define tobacco as an agricultural product that can be freely marketed to persons18 years of age or older.  (If defined as a drug delivery system, cigarettes would be obtainable only with a physician’s prescription, which would essentially prevent, or greatly limit, children’s access to them.)

The Master Settlement Agreement of 1999, that required the tobacco industry to pay the sates 246 billion dollars was able to restrict some forms of youth-oriented advertising and funds anti-smoking education, which may accomplish some of the changes initially proposed.  Unfortunately, during the economic downturn some states have used these funds to meet taxation shortfalls.