Objectives-It has been assumed that nicotine dependence has a slow onset and occurs only after prolonged daily use of tobacco. A cohort of young adolescents was followed to determine when the first symptoms of nicotine dependence occur with respect to the duration and frequency of tobacco use. Design-A cohort of 681 seventh grade students (age 12-13 years) from seven schools in two small cities in central Massachusetts was followed over one year. Detailed information regarding tobacco use was obtained in individual confidential interviews conducted in school three times over the year. The latency time to the onset of symptoms of nicotine dependence was measured from the time a subject first smoked at a frequency of at least once per month. Results-22% of the 95 subjects who had initiated occasional smoking reported a symptom of nicotine dependence within four weeks of initiating monthly smoking. One or more symptoms were reported by 60 (63%) of these 95 subjects. Of the 60 symptomatic subjects, 62% had reported experiencing their first symptom before smoking daily or began smoking daily only upon experiencing their first symptom. Discussion-The first symptoms of nicotine dependence can appear within days to weeks of the onset of occasional use, often before the onset of daily smoking. The existence of three groups of individuals-rapid onset, slower onset, and resistant-distinguishable from one another by their susceptibility to nicotine dependence, is postulated.

Objective: To determine if there is a minimum duration, frequency or quantity of tobacco use required to develop symptoms of dependence. Design and setting: A retrospective/prospective longitudinal study of the natural history of tobacco dependence employing individual interviews conducted three times annually in two urban school systems over 30 months. Detailed histories of tobacco use were obtained including dates, duration, frequency, quantity, patterns of use, types of tobacco, and symptoms of dependence. Participants: A cohort of 679 seventh grade students (age 12-13 years). Main outcome measures: The report of any of 11 symptoms of dependence. Results: Among 332 subjects who had used tobacco, 40% reported symptoms, with a median latency from the onset of monthly smoking of 21 days for girls and 183 days for boys. The median frequency of use at the onset of symptoms was two cigarettes, one day per week. The report of one or more symptoms predicted continued smoking through the end of follow up (odds ratio (OR) 44, 95% confidence interval (CI) 17 to 114, p < 0.001). Conclusions: Symptoms of tobacco dependence commonly develop rapidly after the onset of intermittent smoking, although individuals differ widely in this regard. Girls tend to develop symptoms faster. There does not appear to be a minimum nicotine dose or duration of use as a prerequisite for symptoms to appear. The development of a single symptom strongly predicted continued use, supporting the theory that the loss of autonomy over tobacco use begins with the first symptom of dependence.

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Few prospective studies of smoking initiation have investigated a wide range of time-varying and invariant predictor variables at the individual and contextual levels concurrently. In this study (1999-2005), 877 Canadian students (mean age = 12.7 years) who had never smoked at baseline completed self-report questionnaires on cigarette smoking and 32 predictor variables in 20 survey cycles during secondary school. Height and weight were measured in survey cycles 1, 12, and 19. School administrators completed questionnaires on school tobacco control policies/activities, and trained observers collected data on access to tobacco products in commercial establishments near schools. Younger age, single-parent family status, smoking by parents, siblings, friends, and school staff, stress, impulsivity, lower self-esteem, feeling a need to smoke, not doing well at school, susceptibility to tobacco advertising, alcohol use, use of other tobacco products, and attending a smoking-tolerant school were independent determinants of smoking initiation. Independent determinants of daily smoking onset among initiators of nondaily smoking included smoking by siblings and friends, feeling a need to smoke, susceptibility to tobacco advertising, use of other tobacco products, and self-perceived mental and physical addiction. Adolescent tobacco control programs should address multiple individual and contextual-level risk factors. Strategies that address nicotine dependence symptoms are also needed for adolescents who have already initiated smoking.

Enforcing tobacco-sales laws improved merchants' compliance and reduced illegal sales to minors but did not alter adolescents' perceived access to tobacco or their smoking. Test purchases of tobacco do not accurately reflect adolescents' self-reported access to tobacco, and reducing illegal sales to less than 20 percent of attempts -- the goal of a new federal law-- may not decrease young people's access to or use of tobacco.

Promotions foster positive attitudes, beliefs, and expectations regarding tobacco use. This fosters intentions to use and increases the likelihood of initiation. Greater exposure to promotion leads to higher risk. This is seen in diverse cultures and persists when other risk factors, such as socioeconomic status or parental and peer smoking, are controlled. Causality is the only plausible scientific explanation for the observed data. The evidence satisfies the Hill criteria, indicating that exposure to tobacco promotion causes children to initiate tobacco use.