Addictive Physiology, Not Personality, May Hook Kids On Nicotine

WORCESTER, Mass., Oct. 1 -- Kids whose first reaction to inhaling tobacco smoke is to feel relaxed are more likely to get hooked on cigarettes, researchers here said.

In a four-year prospective study of 1,246 sixth-grade students, two-thirds of those who tried cigarettes and reported a feeling of relaxation became dependent, compared with 28.7% of those who had other reactions, according to Joseph DiFranza, M.D., of the University of Massachusetts Medical School here and colleagues.

The feeling of relaxation was the strongest predictor of dependence, Dr. DiFranza and colleagues reported online in the journal Pediatrics.

"We know that nicotine can have an immediate impact on the brain, and yet we also know that not every adolescent who tries a cigarette gets hooked," Dr. DiFranza said in a statement.

After an earlier study had shown that youths differ widely in their susceptibility to nicotine, Dr. DiFranza and colleagues conducted the Development and Assessment of Nicotine Dependence in Youth 2 (DANDY-2) study.

The goal was to try to account for the "difference in vulnerability among adolescents who pick up that first cigarette," he said.

Students in grade six were followed from January 2002 through January 2006, with 11 waves of face-to-face interviews, usually three per school year. The interviews used two instruments - the 10-item Hooked on Nicotine Checklist, which measures barriers to quitting or "loss of autonomy," and a measure of nicotine dependence based on the definition in the International Classification of Diseases, Tenth Revision (ICD-10).

The researchers attempted to measure 45 variables (including such factors as personality, environment, and reactions to tobacco) but not all could be evaluated because only 217 students actually reported inhaling cigarettes - about half the number that was expected.

But of the students who inhaled, 58.5% reported that tobacco use led to barriers to quitting or "lost autonomy," the researchers found. Barriers included such things as finding it hard to concentrate or feeling irritable when unable to smoke.

Nearly three in 10 first-time inhalers (28.7%) experienced relaxation, and

of those, 90.7% later experienced barriers to quitting, compared with 42.5% of those who did not feel relaxed after the first time. The hazard ratio was 3.26 with a 95% confidence interval from 1.95 to 5.46, which was significant at P<0.001.

Depressed mood was also a significant predictor of loss of autonomy (at P=0.004), while involvement in extracurricular activities, being female, and distractibility were significantly protective, at P=0.045, P=0.01, and P<0.001, respectively.

A similar pattern was seen for full-blown ICD-10 dependence, Dr. DiFranza and colleagues found:

• Kids whose first cigarette left them relaxed were more than twice as likely to become addicted. The hazard ratio was 2.43, with a 95% confidence interval from 1.27 to 4.65, which was significant at P=0 .007.
• Depressed mood remained a significant predictor (at P=0.007) but two other factors also attained significance - awareness of the advertising character Joe Camel (at P=0.02) and having a novelty-seeking personality type (at P=0.02).
• The factors that had been protective against loss of autonomy lost significance, but two others became significant as protectors against dependence: impulsiveness (at P=0.05) and getting along with mother (at P=0.01).

The researchers noted that the Joe Camel advertising campaign was stopped when the study subjects were in the second grade, suggesting that the effects of advertising are long-lasting.

Personality factors often determine who tries smoking, the researchers concluded, but the brain's reaction to nicotine appears to be what determines who gets hooked.

"It appears that it is an addictive physiology and not an addictive personality that determines who will become dependent," Dr. DiFranza said.

The authors noted several limitations of the study, including the fact that their sample may not be representative of other populations. The self-reported nature of the data is also a limitation, as is the fact that first reactions and dependence are subjective.

Other limitations, they said, include the fact that "there may be risk factors for dependence that were not measured; we did not consider potential genetic risk factors; we did not consider the use of alcohol or other drugs; and the data may not describe individuals who begin smoking after adolescence."