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Understanding tobacco addiction
8 November 2011 - Due to the profoundly beneficial effects of potent combination
therapy for HIV, commonly called ART or HAART, life-threatening infections are uncommon in
HIV-positive people who are able to take and adhere to ART in Canada and other high-income
countries. An additional benefit of HIV drug therapy is that HIV-positive people who
have minimal co-existing health conditions and who begin ART today are expected to
have near-normal life spans.
These days, although deaths can still occur among HAART users, they are often unrelated to HIV
infection itself. Rather, they tend to stem from complications affecting the heart, kidneys,
liver and lungs as well as cancers-caused in part by cardiovascular disease, hepatitis and
other viral co-infections, and addictions, including the use of tobacco.
Tobacco smoking is relatively common among HIV-positive people; indeed, some surveys have found
that as much as 50% of an HIV clinic's population are smokers. In contrast, rates of smoking among
HIV-negative adults in Canada have fallen below the 20% level.
Addiction to tobacco can cause devastating health problems, including cardiovascular disease, lung
disease and cancer. Also, smoking harms nearly every organ in the body.
The biology of addiction
Out of the 4,000-plus chemicals in tobacco smoke, one in particular-nicotine-plays a major role
enabling addiction to tobacco. After inhaling tobacco smoke, nicotine quickly enters the blood
and, from there, it rapidly penetrates the brain. Once inside the brain nicotine binds to
receptors. This binding triggers brain cells to release chemical signals associated
with feelings of well-being and even pleasure. Nicotine also provides stimulation
for the brain, and this reduces feelings of stress and anxiety. Repeated bouts
of smoking reinforce these effects of nicotine on the brain, resulting over
time in a powerful addiction. Furthermore, it appears that continued
smoking causes the brain to express more receptors for nicotine,
an effect that helps to intensify and consolidate the drug's hold on smokers.
Nicotine withdrawal
Tobacco users often smoke throughout the day to maintain the concentration of nicotine in their blood.
This minimizes the likelihood of nicotine withdrawal. When a smoker suddenly stops smoking, one or more
of the following symptoms can emerge:
- irritability
- anger
- depressed mood
- restlessness
- anxiety
- difficulty concentrating
- difficulty getting along with friends and family members
- increased feelings of hunger
- difficulty falling asleep
These symptoms of withdrawal underscore nicotine's deep potential for addiction. Furthermore, many
people who quit smoking experience these symptoms-they are a normal part of the quitting process.
The intensity and duration of nicotine withdrawal symptoms vary from one person to another.
Still, all people who are thinking about quitting should first discuss their plans with a
doctor so they can be supported. They also need to let their close friends and family
members know that they will be quitting so that key people in the smoker's life are
aware of impending changes and will be on the lookout for unusual shifts in mood.
Such monitoring is important, as there have been reports of severe depression
in people undergoing nicotine withdrawal.
Social and behavioural aspects of nicotine addiction
According to addiction researcher Neal Benowitz, MD, from the University of California at San
Francisco, drug-taking behaviours are learnt. Over time, Dr. Benowitz notes that the tobacco
smoker "begins to associate specific moods, situations or environmental factors with the
rewarding effects of the drug." These associations help maintain cigarette smoking. As
an example, Dr. Benowitz observed that "people habitually smoke cigarettes in specific
situations such as after a meal, with a cup of coffee or an alcoholic drink, or with
friends who smoke. The association between smoking and these other events repeated
over many times causes the environmental situations to become powerful cues for
the urge to smoke." Even "aspects of the drug-taking process, such as
manipulation of smoking materials, or the taste, smell or feel of
smoke in the throat, become associated with the pleasurable effects of smoking."
Unpleasant moods can become a cue that reinforces smoking. For instance, Dr. Benowitz has found that
smokers "may learn that not having a cigarette provokes irritability, and smoking a cigarette provides
relief. After repeated experiences of this sort, a smoker may come to regard irritability from any
source such as stress or frustration as a cue for smoking."
For these and other reasons, counselling is an important aspect for beginning and sustaining the
process of breaking free from nicotine addiction.
The path to quitting
Quitting smoking ultimately helps to improve health-related quality of life and decreases the risk
for cardiovascular disease and previously mentioned health problems. To help smokers quit, a
combination of counselling with one (or sometimes more) of the following therapies can be useful:
Nicotine replacement therapy - This is available in different formulations, such as chewing gum,
lozenges, inhalers and a skin patch.
Bupropion (Wellbutrin, Zyban) - This drug was first sold as an antidepressant. When doctors noticed
that some of their patients taking bupropion began to spontaneously quit smoking, researchers started
conducting clinical trials to explore this effect of the drug. Bupropion appears to increase chemical
signals in the brain that mimic the effect of nicotine while, at the same time, blocking nicotine
receptors.
Varenicline (Champix, Chantix) - This drug blocks the same receptors used by nicotine and therefore
has similar effects on brain cells.
All three of these therapies offer options that people trying to quit smoking can discuss with their
doctors so that together they can weigh the risks and benefits and find the best path to break free from
tobacco.
In our next CATIE News bulletin we focus on a Canadian clinical trial of varenicline in HIV-positive
people, discussing its safety and effectiveness and provide links to several quitting resources.
-Sean R. Hosein
REFERENCES:
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- Marshall MM, Kirk GD, Caporaso NE, et al. Tobacco use and nicotine dependence among HIV-infected and uninfected injection drug users. Addictive Behaviors . 2011 Jan-Feb;36(1-2):61-7.
- Duval X, Baron G, Garelik D, et al. Living with HIV, antiretroviral treatment experience and tobacco smoking: results from a multisite cross-sectional study. Antiviral Therapy . 2008;13(3):389-97.
- Levine AM, Seaberg EC, Hessol NA, et al. HIV as a risk factor for lung cancer in women: data from the Women's Interagency HIV Study. Journal of Clinical Oncology . 2010 Mar 20;28(9):1514-9.
- Fuster M, Estrada V, Fernandez-Pinilla MC, et al. Smoking cessation in HIV patients: rate of success and associated factors. HIV Medicine . 2009 Nov;10(10):614-9.
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- Palella FJ Jr, Baker RK, Buchacz K, et al. Increased mortality among publicly insured participants in the HIV Outpatient Study despite HAART treatment. AIDS . 2011 Sep 24;25(15):1865-76.
- Aubin HJ, Rollema H, Svensson TH, et al. Smoking, quitting, and psychiatric disease: A review. Neuroscience & Biobehavioral Reviews . 2011 Jun 23. [Epub ahead of print].
- Benowitz NL. Pharmacology of nicotine: addiction, smoking-induced disease, and therapeutics. Annual Review of Pharmacology and Toxicology . 2009;49:57-71.
- Polosa R, Benowitz NL. Treatment of nicotine addiction: present therapeutic options and pipeline developments. Trends in Pharmacological Sciences . 2011 May;32(5):281-9.
- Bacher I, Houle S, Xu X, et al. Monoamine oxidase A binding in the prefrontal and anterior cingulate cortices during acute withdrawal from heavy cigarette smoking. Archives of General Psychiatry . 2011 Aug;68(8):817-26.
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