OBJECTIVE: To extend the findings of the first Development and Assessment of Nicotine Dependence in Youth study by using diagnostic criteria for tobacco dependence and a biochemical measure of nicotine intake. The first study found that symptoms of dependence commonly appeared soon after the onset of intermittent smoking.

DESIGN: A 4-year prospective study.

SETTING: Public schools in 6 Massachusetts communities.

PARTICIPANTS: A cohort of 1246 sixth-grade students.

INTERVENTIONS: Eleven interviews.

MAIN OUTCOME MEASURES: Loss of autonomy over tobacco as measured by the Hooked on Nicotine Checklist, and tobacco dependence as defined in International Classification of Diseases, 10th Revision (ICD-10).

RESULTS: Among the 217 inhalers, 127 lost autonomy over their tobacco use, 10% having done so within 2 days and 25% having done so within 30 days of first inhaling from a cigarette; half had lost autonomy by the time they were smoking 7 cigarettes per month. Among the 83 inhalers who developed ICD-10-defined dependence, half had done so by the time they were smoking 46 cigarettes per month. At the interview following the onset of ICD-10-defined dependence, the median salivary cotinine concentration of current smokers was 5.35 ng/mL, a level that falls well below the cutoff used to distinguish active from passive smokers.

CONCLUSIONS: The most susceptible youths lose autonomy over tobacco within a day or 2 of first inhaling from a cigarette. The appearance of tobacco withdrawal symptoms and failed attempts at cessation can precede daily smoking; ICD-10-defined dependence can precede daily smoking and typically appears before consumption reaches 2 cigarettes per day.