genetic liability (Kendler et al. 2003). Personality traits related to impulsivity also load on this latent genetic factor (Young et al. 2000; Krueger et al. 2002). In fact, twin studies suggest that genetic factors contributing to variation in dimensions of personality, particularly behavioral undercontrol, account for a substantial proportion of the genetic diathesis for alcohol dependence and most of the common genetic diathesis for alcohol dependence and conduct disorder (Slutske et al. 2002). In addition, there are electrophysiological abnormalities observed in alcohol dependent individuals that are also associated with other forms of substance dependence, childhood externalizing disorders and adult antisocial personality disorder (Iacono et al. 1999; Porjesz et al. 2005), again suggesting that an underlying vulnerability toward disinhibition may contribute to a number of different externalizing disorders, of which alcohol dependence is one. Together, these literatures indicate that impulsivity may be a general risk factor for a number of conditions broadly termed the externalizing spectrum (Krueger et al. 2002), and that alcohol use disorders may represent one specific manifestation of this spectrum.
