Adolescent smoking trajectories and nicotine dependence.

The present study correlates empirically constructed prospective adolescent smoking trajectories with indicators of nicotine dependence assessed in adolescence and in adulthood. Excluding individuals who reported no smoking during repeat assessment (nonadopters), we identified five smoking trajectory groups: experimenters (n=116, 48.5%), late increasers (n=39, 16.3%), early increasers (n=37, 15.5%), quitters (n=22, 9.2%), and persistent smokers (n=25, 10.5%). Higher frequency of nicotine dependence symptoms in adolescence occurred in the quitters and persistent smokers groups, who smoked at higher levels relative to the experimenters, late increasers, and early increasers groups, who reported a similar frequency of nicotine dependence symptoms and smoked at low levels. Lifetime nicotine dependence was assessed in adulthood in lifetime daily smokers using the Fagerström Test for Nicotine Dependence (FTND) and the Nicotine Dependence Scale (NDS). Lifetime FTND levels were similar across trajectory groups. Relative to experimenters, all remaining smoking trajectory groups had higher NDS levels that were similar to one another. These results suggest that higher levels of adolescent nicotine dependence were associated with heavier smoking trajectory groups, and that regardless of trajectory group membership, smoking more than a few cigarettes per week throughout adolescence resulted in similar levels of lifetime nicotine dependence as measured by the FTND and NDS.

Environmental and genetic determinants of tobacco use: methodology for a multidisciplinary, longitudinal family-based investigation.

This article describes the ongoing collaborative effort of six research teams to operationalize and execute an integrative approach to the study of gene x environment interactions in the development of tobacco dependence. At the core of the project is a longitudinal investigation of social and behavioral risk factors for tobacco use in individuals who were, on average, 13 years of age at intake and for whom smoking outcomes extending from early adolescence to young adulthood have been characterized previously (current average age of the cohort is 29 years). The conceptual framework for the integrative approach and the longitudinal investigation on which the study is based is presented. A description is also provided of the methods used to: (a) recruit participants and families to provide DNA samples and information on tobacco use; (b) assess participants for relevant tobacco-related phenotypes including smoking history, current use of tobacco, and nicotine metabolism; (c) assess the quality of the DNA samples collected from participants for genome-wide scanning and candidate gene analysis; (d) examine several research questions concerning the role of genetic and environmental factors in the onset and maintenance of tobacco use; and (e) ensure adherence to local and federal guidelines for ethical and legal investigations of genotypic associations with tobacco-related phenotypes in families. This investigation is unique among ongoing studies of the genetics of tobacco dependence in the extent to which equal importance has been assigned to both phenotypic and genotypic measurements.