The Tipping Point: How Little Things Can - By Gladwell, Malcolm Page 0,91

Johnston, who heads the psychiatry division for the company. “You can imagine that someone in my position gets reports about everything, so I didn’t put much stock in them. But I kept getting them. It was very unusual.” This was in 1986, before the depression smoking link was well understood, so the company was initially puzzled. But what they soon realized was that bupropion was functioning as a kind of nicotine substitute. “The dopamine that nicotine releases goes to the prefrontal cortex of the brain,” explains Johnston. “That’s the pleasure center of the brain. It’s what people believe is responsible for the pleasure, the sense of well being, associated with smoking, and that’s one of the reasons it’s so hard to quit. Nicotine also increases norepinephrine, and that’s the reason that when you try to quit smoking and you no longer get so much norepinephrine, you get agitation and irritability. Bupropion does two things. It increases your dopamine, so smokers don’t have the desire to smoke, then it replaces some of the norepinephrine, so they don’t have the agitation, the withdrawal symptoms.”

Glaxo Wellcome has tested the drug—now marketed under the name Zyban—in heavily addicted smokers (more than 15 cigarettes a day) and found remarkable effects. In the study, 23 percent of smokers given a course of anti smoking counseling and a placebo quit after four weeks. Of those given counseling and the nicotine patch, 36 percent had quit after four weeks. The same figure for Zyban, though, was 49 percent, and of those heavily addicted smokers given both Zyban and the patch, 58 percent had quit after a month. Interestingly, Zoloft and Prozac—the serotonin drugs—don’t seem to help smokers to quit. It’s not enough to lift mood, in other words; you have to lift mood in precisely the same way that nicotine does, and only Zyban does that. This is not to say that it is a perfect drug. As with all smoking cessation aids, it has the least success with the heaviest smokers. But what the drug’s initial success has proven is that it is possible to find a sticky Tipping Point with smoking: that by zeroing in on depression, you can exploit a critical vulnerability in the addiction process.

There is a second potential Tipping Point on the stickiness question that becomes apparent if you go back and look again at what happens to teens when they start smoking. In the beginning, when teens first experiment with cigarettes, they are all chippers. They smoke only occasionally. Most of those teens soon quit and never smoke again. A few continue to chip for many years afterward, without becoming addicted. About a third end up as regular smokers. What’s interesting about this period, however, is that it takes about three years for the teens in that last group to go from casual to regular smoking—roughly from fifteen to eighteen years of age—and then for the next five to seven years there is a gradual escalation of their habit. “When someone in high school is smoking on a regular basis, he or she isn’t smoking a pack a day,” Neal Benowitz, an addiction expert at the University of California at San Francisco, says. “It takes until their twenties to get to that level.”

Nicotine addiction, then, is far from an instant development. It takes time for most people to get hooked on cigarettes, and just because teens are smoking at fifteen doesn’t mean that they will inevitably become addicted. You’ve got about three years to stop them. The second, even more intriguing implication of this, is that nicotine addiction isn’t a linear phenomenon. It’s not that if you need one cigarette a day you are a little bit addicted, and if you need two cigarettes a day you are a little bit more addicted, and if you need ten cigarettes you are ten times as addicted as when you needed one cigarette. It suggests, instead, that there is an addiction Tipping Point, a threshold—that if you smoke below a certain number of cigarettes you aren’t addicted at all, but once you go above that magic number you suddenly are. This is another, more complete way of making sense of chippers: they are people who simply never smoke enough to hit that addiction threshold. A hardened smoker, on the other hand, is someone who, at some point, crosses that line.

What is the addiction threshold? Well, no one believes that it is exactly the same for all people. But Benowitz and Jack Henningfield—who are probably