8 November 2011 

Understanding tobacco addiction

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


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