Early course of nicotine dependence in adolescent smokers

Abstract

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.

FIGURE 1

Order of appearance of symptoms of diminished autonomy. The bars show how often (proportion) each symptom type appeared as the first, second, third, or fourth type of symptom to appear in 370 individuals who had ever puffed on a cigarette. Strong desire was the most common first symptom, withdrawal the most common second symptom, feeling addicted the most common third symptom, and difficulty controlling use (“can’t quit”) the most common fourth symptom.

FIGURE 2

Cumulative frequency distribution of development of symptoms of diminished autonomy and smoking frequency (N = 370). The first symptom refers to the first symptom of any type. The upper border of the shaded area represents monthly smoking, and the lower border represents daily smoking. Log-rank tests of differences between curves yielded the following: strong desire versus withdrawal, P = .09; feeling addicted versus difficulty controlling use, P = .8; strong desire versus feeling addicted or difficulty controlling use, P < .01; withdrawal versus feeling addicted, P = .09; withdrawal versus difficulty controlling use, P = .05.

FIGURE 3

Relationship between loss of autonomy and smoking frequency over time. Shown are relative risk (RR) estimates with 95% CIs. The arrows denote the direction of the relationships modeled (eg, whether smoking frequency during round 1 increased the risk of symptoms in round 2). The relationship with frequency of smoking is expressed on a logarithmic scale. For instance, a 1-unit increase in the symptom score in round 2 increased by 6% the number of cigarettes smoked per month in round 3. Each 10-fold increase in the number of cigarettes smoked per month in round 2 increased by 20% the symptom score in round 3.