Parents modelling, peer influence and peer selection impact on adolescent smoking behavior: A longitudinal study in two age cohorts.

Understanding the key factors that influence smoking behavior, especially during adolescence, has a meaningful impact on public health. This study examined the impact of parent modelling, peer influence and peer selection on adolescent smoking behavior in two Portuguese cohorts followed for three years. A questionnaire was delivered in classes and schools randomly selected, three times, one per year (cohort1: time1-7th, time2-8th, time3-9th; cohort2: time1-10th, time2-11th, time3-12th graders). The sample included a total of 656 students (402 younger [time1 Mage = 13.17, SD = 0.53, 63.7% girls;] and 254 older [time 1 Mage = 16.20, SD = 0.53, 65% girls]). Longitudinal data were examined through an autoregressive cross-lagged model (ARCL). The model explained 35% of the variance in smoking behavior at T3 for the global sample (4% for the younger and 58% for the older). Over time, in both cohorts, the percentage of never smokers decreased sharply and the percentage of regular smokers increased rapidly. We observed that participants in the older cohort had higher chances of smoking if their parents smoked. Nevertheless, we did not find a parental modelling effect in the longitudinal model. Peer influence and peer selection influenced smoking behavior. However, peer selection influenced the youngest group, both processes influenced the middle age group, and only peer influence influenced the oldest. Best friend and friends had a stronger impact on the younger while friends and same grade students had a stronger impact on the older. Prevention programs should regard these differences of interpersonal influences through adolescent development and specific strategies for different age groups should be considered.