Early course of nicotine dependence in adolescent smokers.

OBJECTIVE The goal was to characterize the early course of nicotine dependence. METHODS Data were collected from 1246 sixth-graders in a 4-year (2002-2006) prospective study using 11 individual interviews. Subjects were monitored for 10 symptoms of dependence by using the Hooked on Nicotine Checklist. The bidirectional prospective relationship between the intensity of dependence (number of symptoms) and smoking frequency was examined by using cross-lagged analyses. RESULTS Of the 370 subjects who had inhaled from a cigarette, 62% smoked at least once per month, 53% experienced dependence symptoms, and 40% experienced escalation to daily smoking. Smoking frequency predicted the number of dependence symptoms at the next interview, and the number of symptoms predicted reciprocally the observed escalation in smoking frequency. Monthly smoking was a strong risk factor for the development of symptoms (adjusted hazard ratio: 9.9 [95% confidence interval: 6.6-14.8]). A strong desire to smoke was the most common presenting symptom, typically followed by the appearance of symptoms of nicotine withdrawal, escalation to daily smoking, and then reports of feeling addicted or difficulty controlling smoking. The appearance of any dependence symptom increased the risk for daily smoking (hazard ratio: 6.81 [95% confidence interval: 4.4-10.5]). CONCLUSIONS Nondaily tobacco use triggers the emergence of nicotine dependence. Early dependence symptoms promote escalation in smoking frequency and, reciprocally, more-frequent smoking accelerates the appearance of additional symptoms of dependence. As this positive feedback progresses, the symptoms of nicotine dependence present in a typical sequence, with some individual variation.