Nicotine Addiction is Quick in Youths

A young cigarette smoker can begin to feel powerful desires for nicotine within two days of first inhaling, a new study has found, and about half of children who become addicted report symptoms of dependence by the time they are smoking only seven cigarettes a month.
"The importance of this study is that it contradicts what has been the accepted wisdom for many decades," said Dr. Joseph R. DiFranza, the lead author, "which is that people had to smoke at least five cigarettes a day over a long period of time to risk becoming addicted to nicotine. Now, we know that children can be addicted very quickly." Dr. DiFranza is a professor of family medicine at the University of Massachusetts.
The researchers recruited 1,246 sixth-grade volunteers in public schools in Massachusetts, interviewing them 11 times over a four-year period. They also took saliva samples to determine blood levels of nicotine and link them to addictive behavior. At some time during the four years almost a third of the children puffed on a cigarette, more than 17 percent inhaled, and about 7.5 percent used tobacco daily.
Since inhaling is required for sufficient drug delivery to cause dependence, the researchers limited their analysis, published in the July issue of The Archives of Pediatrics and Adolescent Medicine, to the 217 inhalers in the group. Their average age when they first inhaled was 12.8 years. Of these, almost 60 percent had lost some control over their smoking, and 38 percent developed tobacco dependence as defined by the widely used diagnostic manual published by the World Health Organization.
In the 10 percent of children who were most susceptible, cravings began within two days of the first inhalation, and saliva analysis showed that being dependent did not require high blood levels of nicotine throughout the day. In some cases dependence could be diagnosed as early as 13 days after the first smoking episode.
For most inhalers, daily smoking was not required to cause withdrawal symptoms. More than 70 percent had cravings that were difficult to control before they were smoking every day. The biochemical analyses confirmed this: the symptoms of dependence began mostly at the lowest levels of nicotine intake.
"We know very little about the natural history of dependence," said Denise B. Kandel, a professor of sociomedical sciences at Columbia and a widely published addiction researcher who was not involved in the study. "This is really the first study that addresses the issue. Its strength is that DiFranza has followed a community sample of adolescents and interviewed them
every three months, which is very difficult to do. "On the other hand," she continued, "his definition of dependence is based on single symptoms, which may be open to question."
The definition of tobacco addiction is controversial, but the scientists used widely accepted criteria to diagnose dependence and a well-validated questionnaire to determine the extent to which smokers had allowed the habit to dictate their behavior.
The researchers write that it may seem implausible that intermittent smoking could provide relief from withdrawal symptoms. But in fact a single dose of nicotine has effects on the brain that can last as long as a month, and the nicotine obtained from just one or two puffs on a cigarette will occupy half of the brain's nicotinic receptors, the molecules specifically sought by nicotine in tobacco addiction.
The authors acknowledge that some of their data is retrospective and comes from self-reports, which can be unreliable, and that it is not possible to draw conclusions about other populations from their sample. In addition, they did not consider the roles of puberty, alcohol and other drug use. But the study has considerable strengths in measuring frequency and duration of smoking and in collecting exposure data by biochemical analysis as well as by repeated interviews.
"People used to think that long-term heavy use caused addiction," Dr. DiFranza said. "Now, we know it's the other way around: addiction is what causes long-term heavy use."
[NYT]