Longitudinal studies of adolescents have provided rich data on the substantial impact of externalizing symptomatology on the likelihood of early initiation of drinking, heavy drinking and alcohol problems within a developmental framework (Englund et al., 2008; King and Chassin, 2007; Merline et al., 2008; Maggs et al., 2008; Sartor et al., 2007). Some adolescent and twin studies have shown a common genetic liability to traits underlying the spectrum of externalizing psychopathology (Dick et al., 2008, 2009; Esposito-Smythers et al., 2009; Hicks et al., 2007a; Iacono and McGue, 2006). Other, though, suggest that some genetic linkages are specific to alcohol dependence (Kendler et al., 2006) and that nongenetic factors may be as important as genetic factors in accounting for co-occurrence of alcohol problems and other externalizing behaviors, at least among women (Hicks et al., 2007b; Knopik et al., 2009).
