“…A number of studies have shown that having parents or siblings who smoke or use illegal drugs in the family increases one's risk of regular smoking (Alexender et al, 1983;Brook et al, 2004;Chassin, Clark, Presson, Sherman, & McGrew, 1986;Denton & Kampfe, 1994;Kierker, Avenevoli, Merikangas, Flaherty, & Stolar, 2001;Eckhardt, Woodruff, & Elder, 1994;Fagan, Brook, Rubenstone, & Zhang, 2005;Flay et al, 1994;Jackson & Henriksen, 1997;Nyari, Heredi, & Parker, 2005;Ohannessian et al, 2004). 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).…”