Milestones in the natural course of onset of cigarette use among adolescents

Abstract

Background: The natural course of onset of cigarette use has been conceptualized as progressing sequentially through 5 stages (preparation, trying, irregular use, regular use, nicotine-dependent smoking). However, recent studies suggest that symptoms of nicotine dependence can occur early in the onset process, raising questions about the validity of this model. The objective of our study was to describe the sequence and timing of 12 milestones (6 related to cigarette use and 6 to symptoms of nicotine dependence) during onset of cigarette use.

Methods: Grade 7 students in 10 secondary schools in Montréal (n = 1293) were followed prospectively every 3-4 months for 5 years. Using Kaplan-Meier analysis, we computed the number of months after first puff at which the cumulative probability of attaining each milestone was 25%, among 311 participants who initiated cigarette use during follow-up.

Results: Inhalation rapidly followed first puff. The cumulative probability of inhalation was 25% at 1.5 months (95% confidence interval [CI] 1.5-2.5). The cumulative probability (and 95% CI) was 2.5 months (1.5-2.5) for mental addiction, 2.5 (1.0-3.0) for smoking a whole cigarette, 4.5 (2.5-8.8) for cravings, 5.4 (3.8-9.7) for physical addiction, 8.8 (7.0-11.9) for monthly smoking, 11.0 (6.4-16.8) for withdrawal symptoms, 13.0 (10.3-20.5) for tolerance, 19.4 (14.5-31.7) for weekly smoking, 19.5 (14.0-23.9) for lifetime total of 100 cigarettes, 23.1 (19.7-37.6) for daily smoking and 40.6 (35.1-56.0) for conversion to tobacco dependence.

Interpretation: Symptoms of nicotine dependence develop soon after first puff and can precede monthly, weekly and daily smoking. Cessation interventions that manage dependence symptoms may be needed soon after first puff.

Fig. 1: Flow of participants through the study. NDIT = McGill University Study on the Natural History of Nicotine Dependence in Teens.

Fig. 2: Cumulative probability of attaining milestones of onset of cigarette smoking from time since initiation among 311 participants who were nonsmokers at baseline and who initiated cigarette smoking during follow-up. See Methods for definitions of the milestones. *Thirty-six subjects reported mental addiction and 15 reported physical addiction before initiation. These subjects were considered to be incident cases at baseline; they contributed zero person-months to the denominator in the computation of time at risk for selected milestone.

Fig. 3: Number of months after initiation of cigarette smoking (first puff) at which the probability of attaining each milestone is 25%. Error bars represent 95% confidence intervals. (See Methods for definitions of the milestones.)