Twin studies have robustly demonstrated that alcohol dependence, other drug dependence, adult antisocial behavior, and childhood conduct disorder overlap in large part due to a shared genetic factor (Kendler et al., 2003a; Krueger et al., 2002; Young et al., 2000). Electrophysiological endophenotypes, which are strongly genetically influenced (van Beijsterveldt et al., 1996), have been shown to capture the shared susceptibility across these disorders (Iacono et al., 1999; Porjesz et al., 2005), again suggesting a shared etiological connection. What is phenotypically common across these disorders is impaired impulse control, as reflected in two of the criteria for the diagnosis of alcohol dependence: (a) the inability to control the amount of alcohol consumed (or the amount of time spent drinking), and (b) continued drinking despite adverse health-related consequences (Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition — DSM-IV; APA, 2000), and one criterion for antisocial personality disorder stating ‘Impulsivity or failure to plan ahead’ (DSM-IV; APA, 2000). Accordingly, it has been hypothesized that the shared element across these disorders comprises a general predisposition to impulsivity. Alternatively, this shared factor has been
