Measures of interest include smoking frequency (number of days out of the past 30 on which the adolescent smoked), smoking quantity (number of cigarettes smoked in the past 7 days), nicotine dependence syndrome scale (NDSS; mean of 10 nicotine dependence items assessed on a four-point Likert-type scale) modified for use in adolescents (Sterling et al., 2009), and gender. Smoking frequency, smoking quantity, and NDSS score were assessed at each follow-up assessment. Additionally, a categorical variable indicating the assessment (baseline, 6, 15, or 24 month follow-up) is included in the repeated-measures analyses.
