 for the link between smoking and depression, according to data collected on nearly 1,500 pairs of female twins. "The twin data show that whatever gene puts you at risk for depression, the same gene puts you at risk for smoking," says Alexander Glassman.
Further evidence for this conclusion comes from a prospective epidemiological study, in which 1,200 people in their twenties were surveyed twice; 18 months to two years apart. Nonsmokers who were depressed at the first interview were more likely to be smoking at the time of the second, while nondepressed smokers were more likely to have become depressed by then.
Genetics may even play a role in how you smoke. Shiftman studied a group of people who had smoked regularly but lightly, five cigarettes or less, four days or more a week, for several years at least. Says Saul Shiftman: "They had ample opportunity to become addicted—on average, they'd smoked 46,000 cigarettes, but we found not the slightest evidence of dependence: they showed no signs of withdrawal when abstinent. They really could casually take smoking or leave it."
Such nonaddicted users—chippers," in drug culture parlance—are also seen among consumers of hard drugs. "We didn't delve deeply into what made these smokers different," says Shiftman. "But we did find evidence that they also had relatives who smoked with little dependence, who followed the same pattern. This makes it plausible, although it doesn't prove that these folks are biologically different." With rare exceptions, chippers have always smoked that way, he points out. For a once-addicted smoker to try to become a chipper is "a risky business" that's probably doomed to failure.
Smoking just doesn't have the cachet it once did. Instead of a mark of worldliness and joie de vivre, it's become something of a social disease. Except on billboards and in magazine ads, the smoker him- or herself is less likely to be the object of admiration than of pity and contempt.
The change in smoking's status is no doubt in part responsible for the 40 percent decline in its prevalence since 1964. And it would seem logical that those people who are still smoking in the face of such adversity are an increasingly hard-core, heavily addicted bunch, unable to quit.
Alexander Glassman conjectures that as the social environment grows more hostile to smoking, the genetic component of the behavior will become more evident. And as the number of smokers drops, an increasing percentage will have psychiatric problems, particularly depression.
But the change hasn't yet been documented. "Actually, I don't think the data support the idea that today's smokers are very different from years back," says Fiore. "The average number of cigarettes they smoke today isn't dramatically different from 20 years ago—about 22 per day."
One thing that has happened is a change in the sociodemographics of smoking. "More and more, it's a behavior predominantly exercised by disadvantaged members of society: 40 percent of high-school dropouts smoke, compared to 14 percent of college grads. Poor people are more likely to smoke than wealthy. It's getting marginalized," he says.
If nothing else, today's antismoking climate has eliminated much denial about the true nature of the cigarette habit. "Smokers are much more aware of being hooked," says Saul Shiftman. "You can't tell how dependent you are if access is easy. If you can smoke at your desk and at a restaurant, you can delude yourself, as people have for decades: 'I like to smoke but I can take it or leave it.' It's hard to say that when the only place you can smoke is outside when it's hailing and 20 degrees."