The phenotypes of alcohol dependence, conduct disorder, and suicide attempts, which show linkage on chromosome 2, are all characterized by elements of impulsivity and behavioral under-control. Conduct disorder is a robust predictor of both concurrent and future alcohol problems [Crowley et al., 1998; Moss and Lynch, 2001; White et al., 2001]. Furthermore, numerous twin studies indicate that the overlap between childhood conduct disorder and adult alcohol dependence is largely due to shared genetic factors [Slutske et al., 1998; Krueger, 1999; Young et al., 2000; Kendler et al., 2003]. This common genetic liability is thought to be a predisposition toward behavioral undercontrol/disinhibition, which can manifest as conduct disorder in childhood and alcohol dependence later in life [Slutske et al., 2002]. It has been demonstrated that GABRA2, a gene associated with alcohol dependence in adults [Edenberg et al., 2004; Lappalainen et al., 2005; Enoch, 2008; Soyka et al., 2008] is associated with CD symptoms and externalizing behavior in adolescents [Dick et al., 2006, 2009], providing evidence that variations in one gene can manifest as different conditions at different stages of the life
