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Risk factors for tobacco dependence in adolescent smokers
  1. I Karp1,*,
  2. J O’Loughlin1,,
  3. J Hanley1,
  4. R F Tyndale2,
  5. G Paradis1,
  1. 1Department of Epidemiology, Biostatistics, and Occupational Health, Faculty of Medicine, McGill University, Montréal, Québec, Canada
  2. 2Department of Pharmacology, University of Toronto, Toronto, Ontario, Canada
  1. Correspondence to:
 Dr Jennifer O’Loughlin
 Department of Epidemiology, Biostatistics, and Occupational Health, McGill University, 1020 Pine Avenue West, Montreal, Quebec H3A 1A2, Canada; jennifer.oloughlin{at}


Objective: To study the incidence of conversion to tobacco dependence (TD) and the prevalence of the TD state in relation to several potential determinants in a sample of adolescent smokers.

Methods: Questionnaires were administered every 3–4 months to document TD symptoms, amount of cigarette consumption, and depression symptoms in a prospective cohort of 1293 grade 7 students in a convenience sample of 10 schools.

Results: Over 54 months of follow-up, 113 of 344 novice smokers converted to TD. The referent series for the analysis of incidence comprised 823 person-surveys. The prevalence series included 1673 person-surveys, contributed by 429 smokers. Conversion to TD and TD status were associated with the intensity of recent (that is, past 3-month) cigarette consumption (adjusted incidence rate ratio (aIRR) 1.63 (95% confidence interval (CI) 1.36 to 1.97) and adjusted prevalence odds ratio (aPOR) 1.35 (95% CI 1.23 to 2.48) per 100 cigarettes per month), slowest CYP2A6 activity (aIRR 4.19 (95% CI 1.38 to 12.76) and aPOR 2.30 (95% CI 1.29 to 4.09)), depression score (aIRR 1.61 (95% CI 1.17 to 2.21) and aPOR 1.47 (95% CI 1.22, 1.75) per 1-unit change). Additional determinants included, for conversion to TD, time since onset of cigarette use (aIRR 0.76 (95% CI 0.58 to 1.00) per year) and, for the TD state, positive TD status six months ago (aPOR 3.53 (95% CI 2.41 to 5.19)).

Conclusions: TD risk in adolescents is associated with intensity of recent cigarette consumption, while the role of more distant cigarette consumption appears small; subjects with slow nicotine metabolism and those with more depression symptoms are at increased risk of becoming tobacco dependent. The risk of being tobacco dependent is considerably higher in subjects who had previously developed the TD state.

  • aIRR, adjusted incidence rate ratio
  • aPOR, adjusted prevalence odds ratio
  • CI, confidence interval
  • GEE, generalised estimating equation
  • OR, odds ratio
  • NDIT, Natural History of Nicotine Dependence Study
  • SE, standard error
  • TD, tobacco dependence
  • tobacco dependence
  • tobacco use disorder
  • smoking
  • risk factors
  • adolescent

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  • * Also Division of Clinical Epidemiology, Montreal General Hospital, Montréal, Québec, Canada

  • Also Institut national de santé publique du Québec, Montréal, Québec, Canada

  • Also Centre for Addiction and Mental Health, Toronto, Ontario, Canada

  • Competing interests: Rachel F Tyndale is a shareholder in Nicogen Research Inc, a company focused on the development of novel smoking cessation treatments.