“…Although modeling is often cited as the reason for the observed link between smoking among family members, genetic effects may also be at play (Boomsma, Koopmans, Van Doornen, & Orlebeke, 1994;Maes et al, 1999). In addition, having friends who smoke or use illegal drugs greatly increases the likelihood of regular smoking in adolescence, continuing through to adulthood (Chassin et al, 2000;Flay, d'Avernas, Best, Kersell, & Ryan, 1983;Griffin, Botvin, Scheier, Doyle, & Williams, 2003;Orlando et al, 2004;Palmer, 1970;Robinson, Klesges, Zbikowski, & Glaser, 1997).…”