Smoking and The Neurobiology of Quitting

     Mark Twain said “Quitting smoking is easy. I’ve done it a thousand times” (6). I have been a smoker on and off for about four years. Two years ago I was able to quit for six months and since then have been able to go up to a month without smoking before reverting back to my nasty habit. Cigarette smoking provides a perfect example of different parts of the nervous system conflicting in goals and their influence on behavior. I ultimately want to quit, a desire pursued by my I-function, but often give in to other impulses and desires that are governed by other brain constructs. I spoke to my physician about possible medications to aid the process, and much to my surprise she (unofficially) advised me not to quit this month while I had a lot to deal with. Making such a significant life change, she said, would be incredibly stressful on my system, and she suggested that I should do so at a less hectic time. I wondered how it could be overall more beneficial for me to continue inhaling poison into my lungs. This sparked an interest in how cigarette addiction affects the nervous system, why it is so hard to quit, and what happens neurobiologically when a smoker quits. Nicotine addiction provides a particularly interesting example of the interplay between different aspects of the nervous system. In terms of smoking behavior certain constructs in the brain seems inherently more predictive of whether quitting will be successful than personal motivation, calling into question the power of the I-function in confronting nicotine and other forms of addiction. Nevertheless, measures taken to affect the I-function like social support and cognitive strategies seem at least as useful as medication in treating addiction.

Nicotine addiction has been classified by the DSM-IV as an illness characterized by tolerance to nicotine, (requiring greater doses to obtain the same effects), withdrawal symptoms following cessation, difficulty quitting, considerable time spent smoking or buying cigarettes, postponing daily life events in order to smoke, and continuing to smoke in spite of health risks (3). Cigarette smoking is the most avoidable major cause of death in the world, and a major cause of premature death in North America, accounting for 5 million fatalities each year as the second-leading cause of death. It can also contribute to other diseases such as respiratory bronchitis, low birth weight, and perinatal mortality, and will cost governments an estimated US $200 billion per year (3). It seems counterintuitive that the fear of death and illness would be insufficient to motivate people to stop or never start. A simple reason for people’s inability to quit is that nicotine is addictive. Nicotine has been classified by scientists as meeting all the criteria of a highly addictive drug (3). According to DSM-IV health standards of chemical dependence, 87-90% of nicotine users suffer from addiction while only 15% of regular cocaine users are addicted to cocaine (2), and nicotine has been ranked ahead of alcohol, cocaine and heroin in dependence (3). Mr. N. A. Photiades wrote to the Times of London in 1957 about his experiences in World War II in which he witnessed men who starved to death because they sold their food for cigarettes (1). The addictive power of nicotine should not be underestimated.

The reasons for smoking are numerous and complicated. Some factors that influence smoking behavior maintenance include in addition to nicotine dependence, genetics, and psychosocial factors (3). Understanding of the mechanisms underlying nicotine addiction has allowed for greater insight into these factors. Nicotine releases hormones acting on various receptors in the brain. Its intake leads to more efficient processing of information and reduced fatigue, as well as sedation, reduced anxiety and euphoria. These effects arise through stimulation of the hypothalamic-pituitary axis which in turn stimulates the endocrine system (3). Research has explored ways in which nicotine can increase proficiency on some tasks. For example, nonsmokers given a dose of nicotine have been shown to tap on a keyboard roughly 5% faster under its influence. In another study, smokers were better at maintaining concentration on a boring 80-minute test than nonsmokers(1). Nicotine also affects stress hormones and causes greater relaxation by stimulating hypothalamic corticotropin-releasing factor (CRF) and increasing levels of endorphins (natural opiates), adrenocortcotropic hormone (ACTH) and arganine vasopressin. Nicotine paradoxically also increases heart rate and blood pressure (3) which in turn causes greater alertness and faster thinking (5). Thus, nicotine affects the brain by inducing both stimulation and relaxation, leading some scientists to conceptualize nicotine as a drug that returns people to a state of psychological neutrality, whether it be from a state of stress or boredom (1). Generally, larger doses are associated with sedation while smaller doses lead to arousal (1, 3). Thus nicotine provides a means of almost immediately affecting one’s level of arousal, reaching the brain in only seven to ten seconds, twice as quickly as intravenous drugs and three times faster than alcohol (5). Many of these more pleasant consequences of mood and performance associated with smoking suggest some motivational factors that prevent quitting.

What makes these effects most compelling is the fact that they operate on brain reward mechanisms, indirectly by means of endogonous opioid activity and directly in dopamine pathways (3) in such a way that the act of smoking reinforces addiction. Dopamine is a brain chemical involved in motivation, learning, and memory, guiding our attention towards information needed for survival. Nicotine, like other drugs, causes five to ten times as much dopamine to move through the nucleus accumbens, focusing the brain’s motivational and attentional resources completely on the drug. Over time a drug addict’s brain adapts to this increased circulation of dopamine by suppressing the dopamine system, causing him to react less strongly to input that would otherwise command his attention, like food, romantic passion, and money. Addicts also have been shown to have fewer dopamine receptors, resulting in a less sensitive system that needs more and more of the drug to feel aroused at all. Addiction also causes the prefrontal cortex, a part of the brain involved with judgment and inhibitory control, to stop functioning normally. Thus nicotine addiction produces a combination of motivation for the drug and impaired behavioral control. Also, greater doses of nicotine are needed to maintain the effects of stimulation (4). Thus the addiction maintains and feeds itself.

Genetic factors have also been shown to affect dopamine sensitivity, as some people are born with fewer dopamine receptors, making them particularly susceptible to enjoying addictive drugs. Research into the dopamine systems has suggested that dopamine sensitivity and addiction are influenced as well by social interactions and context. Studies have found that monkeys that lose social status also lose dopamine receptors, suggesting that social rejection can lead to greater susceptibility to addiction. Also, it is likely that the environmental factors can influence people’s susceptibility to acquiring addictive habits, smoking or otherwise, including social network and availability of the drug. Volkow, the leading pioneer of salience theory of dopamine (cited above), believes that being in a stimulating environment that provides other meaningful sources of engagement can make people less inclined to seek drug-induced boosts (4). Others have posited that nicotine serves other functions in someone’s life other than those occurring at the neurobiological level. Some evidence suggests that smokers find the habit useful in maintaining daily habits like work. A study from the 1970s by Meade and Wald interviewed 3,600 workers on their smoking habits and found that these participants smoked most of their daily cigarettes while at their jobs (1), suggesting that certain behavioral patterns and choices enforce smoking beyond the level of neurobiology.

A consideration of symptoms associated with withdrawal allow for a clearer picture of nicotine’s addictive power. One particularly frustrating consequence is difficulty with concentration (2). This is a result of low blood sugar arising from the fact that in smokers nicotine has some level of control over regulation of brain glucose levels by means of adrenaline that releases stored sugars and fats, and when smokers quit their systems have to adjust and resume control over glucose production. Other withdrawal symptoms include nervousness, headaches, weight gain from increased appetite, decreased heart rate, insomnia, irritability, and depression, all of which peak in the first few days but are generally gone within a month (3). A consideration of these outcomes in conjunction with the positive effects induced by smoking provides ample explanation for the physiological stress caused by quitting.

A brief consideration of the treatment methods suggest that neurobiological approaches alone are not enough. While methods such as nicotine replacement therapy, nicotine patches, and varenicline (a partical agonist for certain receptors that prevents nicotine binding) have been shown to be effective (3) some researchers believe that the single best predictor of success with quitting is the amount of face-to-face encouragement quitters receive from physicians, friends, and relatives (5). Environmental factors play in importantly as well, particularly whether those around someone smokes. Almost 75% of people who quit relapse in the presence of people who are smoking. What seems most predictive of people’s ability to quit seems to rest on the extent to which they develop a system of coping strategies (1) involving both cognitive and behavioral approaches. Cognitive strategies include thinking consciously about the benefits of quitting or other motivating realities like people who have died from smoking. Behavioral strategies involve removing oneself from tempting situations or performing distracter tasks like video games when cravings hit (1). A website designed to motivate people to quit smoking attests that a major factor aiding the process is education and understanding (2). These researchers seem to believe that increased understanding of what to expect from withdrawal systems will ease the process. Perhaps if the I-function feels a greater level of control over what is happening then the effects of withdrawal will be minimized. The website goes on to make empowering statements designed to give people a greater sense of autonomy over their addictions and abilities to quit. I find myself somewhat compelled by these statements. In fact, both hypnosis and acupuncture treatments have been found to show effectiveness likened to that of placebo (3), and both professional group therapy or counseling has shown a 60-100% initial cessation rate and a 20% 1-year cessation rate. All of these methods rely on the importance of the I-function inhibiting addiction: believing in the ability to quit as well as having the adequate social support seem to fulfill this goal seem highly important in quitting, even if the experience of addiction is largely due to the brain and dopamine.

All of this research makes me see that quitting will involve a strong effort to override some very central processes of my nervous system functioning. Information about situational factors I can manipulate to my advantage and knowledge of details of withdrawal symptoms, including factors predicting their duration, has also made me confident that I and my I-function will be able to overcome this addiction.

1) http://www.acsh.org/healthissues/newsid.798/healthissue_detail.asp

2) http://www.whyquit.com/whyquit/

3) http://www.emedicine.com/med/topic1642.html

4) http://groups.msn.com/FreedomFromTobaccoQuitSmokingNow/addiction.msnw?action=get_message&mview=0&ID_Message=256152&LastModified=4675572759122348559

5) http://www.time.com/time/magazine/article/0,9171,967523,00.html

6) http://www.quitsmokingsupport.com/hardtoquit.htm