Smoking “hijacks” the reward systems in the brain that drive you to seek food, water and sex, driving you to seek nicotine with the same urgency. Your brain thinks that this has to do with survival of the species.

Nicotine isn’t equally addictive for everyone. A lot of people do not smoke because they never liked it to begin with. Then there are “chippers,” who smoke occasionally but never seem to get hooked. But most people who smoke will eventually do it all day, every day.

New discoveries in genetics may explain why certain people take to smoking with such goes to and end up so addicted. Some people, for instance, produce a gene-encoded enzyme that clears nicotine from their bloodstreams rapidly, so they tend to smoke more and develop stronger addictions. Others possess special receptors in the brain that bond extra tightly with nicotine, giving them an especially intense high that makes it harder to quit.

Drug makers are exploiting the science of addiction to create novel treatments to help smokers stop. The newest stop-smoking medication, the first to be approved in 10 years, is called Chantix. Available by prescription, Chantix masquerades as nicotine well enough to occupy the brain’s nicotine receptors, where it may lessen cravings. Real nicotine, when it comes along, cannot find enough free receptors to do its thing.

Chantix seems to have a higher success rate than Zyban, an antidepressant that helps to balance dopamine levels. And recently released federal guidelines to doctors for helping smokers quit reported that the drug, combined with the nicotine replacement patch and use of nicotine nasal spray or gum as needed, produced higher long-term abstinence than the patch alone.

Doctors have written millions of prescriptions for Chantix, though enthusiasm for the drug was tempered by reports of suicide and bizarre behaviors in people taking it. The reports prompted the Food and Drug Administration to issue a safety warning about Chantix early in 2008.

Continued research should help to resolve lingering concerns about the safety of Chantix. Meanwhile, experts continue to recommend the old standbys: nicotine replacement gums, patches, nasal sprays, inhalers and lozenges, which have been proved to be safe.

Nicotine by itself does not cause cancer, heart disease or other major health problems linked to smoking; other chemicals in tobacco smoke are to blame. Nicotine replacement can be used alone or with prescription medications or, for best results, combined with counseling. Recent evidence suggests that using two forms simultaneously, like the patch and gum together, works better than either alone.

Although nicotine replacement products do not require a prescription, the F.D.A. limits where and how they are sold. They are also expensive.

Still, no treatment works for everyone. And even with the most successful treatments, only about 30 percent of attempts to stop last more than six months. Compared with willpower alone, however, that’s a huge improvement. Fewer than one in 10 smokers who go it alone manages to go six months without a cigarette. Most do not make it past a week.
When longtime smokers finally do stop, they soon realize that not smoking doesn’t necessarily make them nonsmokers. That’s what counseling is for — learning to function without nicotine and to cope with the cues that trigger smoking urges.

Most important, former smokers have to rediscover that it is possible to enjoy life without cigarettes, although the yearning may never die completely.