Study finds teens hooked after fewer cigarettes over shorter period than previously expected

August 29, 2002

WORCESTER, Mass.-A startling new study published today in the international journal Tobacco Control shows that kids typically get hooked on nicotine with alarming speed and at levels of tobacco use that are so low that few researchers had even considered addiction possible.

Because adults who are hooked on nicotine generally smoke at least ten cigarettes every day, scientists have always assumed that a person could not become hooked until he or she smoked at least that much.  It usually takes a few years for young smokers to progress to smoking ten cigarettes per day so it was also assumed that nicotine dependence was very slow to develop.  The study, however, indicated that just the opposite is true: kids get hooked more quickly while smoking much less.

The results of the study, published in the journal’s September issue, surprised even the researchers themselves. "I expected that some kids would get hooked quickly, but I thought that the average kid would have to smoke for a few years to get hooked," admitted Joseph R. DiFranza, MD, professor of family medicine & community health at the University of Massachusetts Medical School (UMMS) and lead author of the study.  "I thought that kids who got hooked quickly would be the exception to the rule.  As it turned out, the kids who did not get hooked quickly were the exception."   The study was sponsored by the National Cancer Institute and conducted by a team of researchers at UMMS, the University of London and Harvard University. 

The study showed that for the teenage girls who got hooked, it took only an average of three weeks from when they started to smoke occasionally.  Among the boys who got hooked, half were hooked within six months of the start of occasional smoking.  "Some of these kids were hooked within a few days of starting to smoke," reported Dr. DiFranza.  "We are unable to explain why girls get hooked faster but we have begun a new study sponsored by the National Institute on Drug Abuse to explore the differences between the sexes." 

Perhaps even more surprising than the speed with which symptoms of addiction appeared was the very small amount of tobacco required.  At the time when they first got hooked, the young smokers were typically smoking only one day per week, averaging only two cigarettes per week.  This contradicts the assumption that addiction does not begin until youths are smoking at least ten cigarettes per day.  In two thirds of the cases, addiction had appeared prior to daily smoking.  This means that youths who have never smoked as much as one cigarette per day are finding it very difficult to quit when they try. 

DiFranza commented: "It’s startling to find that kids who are smoking two cigarettes per week need help to overcome a dependency on nicotine but the data shows that youths who showed signs of being hooked at these very low levels of consumption were 44 times more likely to be still smoking at the end of the study."  Previous research has shown that it takes the average teenage smoker 18 years to break the habit for good.

After the addiction begins, a growing tolerance to the effects of nicotine requires the addicted smoker to gradually smoke more and more.  The common wisdom had been that tolerance to nicotine must precede the addiction.  The study results suggest that the opposite is true, that the addiction comes first.

In order to determine how long it takes for kids to get hooked, the researchers followed 679 seventh grade students over a period of 30 months.  The research subjects were interviewed in great detail eight times over the course of the study.  Among 332 youths who had ever used tobacco, 40% reported symptoms of addiction.

“This study has overturned a lot of conventional wisdom,” DiFranza said.  Addiction to tobacco does not require daily smoking, heavy smoking or prolonged smoking, and tolerance to nicotine doesn’t precede addiction, it follows it.  Researchers are now scrambling to determine the effects of small intermittent doses of nicotine on the brain.  Already, one such study has concluded that a single exposure to nicotine has long lasting effects on the brain. 

The authors coin a new term, "juvenile onset nicotine dependence" to emphasize that children are different from adults when it come to the effects of nicotine.  The authors site previous research showing that people who begin to smoke as adolescents are more likely to get hooked, to have greater difficulty quitting, to smoke for a greater number of years and to smoke more heavily as adults.  The brain does not stop growing at birth; brain development continues into adolescence.  The fact that the adolescent brain is still developing may make adolescents more vulnerable to addiction than adults.  Animal research has shown that at doses seen with smoking, nicotine causes brain damage in adolescent animals that is not seen in adult animals.  The impact of nicotine on the brain is also stronger and longer lasting in adolescents.

The study's authors also note that it has been known for several decades that a physical dependence to narcotics can develop after a single dose of morphine.  "A convergence of data from human and animal studies leads me to suspect that addiction to nicotine begins, in many cases, with the first cigarette," commented DiFranza.

The University of Massachusetts Medical School is one of the fastest growing academic health centers in the country, attracting more than $131 million in research funding annually.  Ranked fifth in the annual US News & World Report ranking of primary care medical schools, UMMS is a leader in health sciences education, research, clinical care and public service.

Joseph R. DiFranza, MD, 508-856-5658

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