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Study Explains Ex-Smokers' Ever-Burning Desire

Sustained tolerance to nicotine key to high relapse rate

WEDNESDAY, Nov. 14, 2001 (HealthDayNews) -- As many people are about to learn during the 25th annual Great American Smokeout tomorrow, giving up cigarettes isn't easy. But staying off them is much tougher, and a new study may shed some light on why smokers so easily return to the habit even years after they quit.

The key may lie in our tolerance to nicotine, which doesn't appear to change even years after we stop smoking, say researchers at the University of Pittsburgh School of Medicine.

"Tolerance … can explain why someone can rapidly go back to a pack a day, even after not smoking for a long time," says study author Dr. Kenneth Perkins, a professor of psychiatry at Pitt.

Perkins says most people don't get hooked on cigarettes when they first start smoking because their tolerance to nicotine is low, meaning their sensitivity to this drug is high. "They can smoke a few cigarettes, feel satisfied and not have to smoke any more," says Perkins.

However, he says the longer you smoke, the more tolerant you become to the effects of nicotine. This means it takes more and more cigarettes to give you the same feeling of satisfaction. And that helps create the habit.

"Tolerance is related to dependence. … You become tolerant to a drug, [and] you need to take more and more of it to get the same effect, and changes that occur due to that lead to dependence," says Perkins.

In the past, researchers believed that once we quit cigarettes, our tolerance to nicotine dropped, meaning our sensitivity increased.

However, the new study shows once we are hooked on smoking, our tolerance to nicotine never declines, even years after not smoking. Should we go back to smoking, this sustained elevation allows us to develop a full-blown habit much faster than we did when we first started to smoke, the researchers say.

"What this research is showing us is you can't go home. Once you start smoking, you are going to experience changes in the way your body responds to nicotine, and those changes are permanent," says Daniel Seidman, director of the Columbia University Tobacco Cessation Clinic and assistant professor at the Columbia University Behavioral Medicine Program.

"What we still don't know, however, is what other implications these permanent changes might have on our overall brain chemistry, and how those changes could be affecting a smoker's overall health," says Seidman.

The small but significant research project actually involved three separate studies of nicotine tolerance in three groups of smokers at various stages of quitting. All were subjected to a series of tests designed to measure tolerance to nicotine, including cardiovascular, behavioral and mood changes.

In the first study, seven smokers who did not want to quit agreed to do so for one week. During intense one-on-one sessions, they were evaluated before stopping, then day by day over a five-day quit program, and then again two days after they resumed smoking.

The second study included 36 participants who wanted to quit smoking. They were evaluated before quitting and three weeks after they stopped smoking. During that time, 24 quit smoking and 12 continued to smoke. The 12 participants who continued to smoke also were used for comparisons.

In a third study, 17 longtime ex-smokers were tested and divided into two groups, one for those who had not smoked for one to four years, and the other for those who had not smoked for six to 19 years before the study started.

For participants in all groups, weight-dependent dosing of nicotine nasal spray was used to document the tolerance to nicotine.

The surprising result: All three groups had essentially the same nicotine tolerance response level, whether they were current smokers, recent quitters or had been smoke-free for up to 20 years.

"We did not expect the tolerance levels to nicotine to be so permanent. It shows that once you become hooked on cigarettes, your response to nicotine can never return to the pre-smoking state," say Perkins.

The study appears in the November issue of the journal Psychopharmacology.

What To Do

"The best thing you can do is never start smoking, because here is good evidence that first, it causes permanent changes in your brain chemistry, and second, those changes help encourage susceptibility to smoking for the rest of your life," says Seidman.

The next best advice: If you are lucky enough to have successfully quit, don't kid yourself into thinking you can resume a "casual" habit. With brain chemistry already "pre-wired" to smoke, Perkins says it may not take much for your old habit to kick in.

For tips and information to help you start kicking the habit, visit QuitNet.

You can also visit the home page for the American Cancer Society's 25th annual Great American Smokeout, which takes place tomorrow.

SOURCES: Interviews with Kenneth Perkins, M.D., professor of psychiatry, University of Pittsburgh School of Medicine; Daniel Seidman, Ph.D., director, Columbia University Tobacco Cessation Clinic and assistant professor, Columbia University Behavioral Medicine Program, New York City; November 2001 Psychopharmacology
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