Poor impulse control is a key risk factor that often underlies suicidal and substance use behaviors (Apter et al. 1995; Beautrais et al. 1999; Brent et al. 1988; Dougherty et al. 2004b, 2004c). Poor impulse control is an important feature of both externalizing behaviors (e.g. Conduct Disorder; Daderman, 1999; Dougherty et al. 2003a, 2003b; Gorenstein and Newman, 1980; Klein et al. 1997; Milich and Kramer, 1984; Tranah et al. 1998) and substance use (Dougherty et al. 2004b; Moeller et al. 2002b). Poor impulse control has been linked to the phenomenology, neurobiology, and familial transmission of suicidal behavior (Brent et al. 1996, 2002, 2003, Mann, 1998; Mann et al. 1999), and to adolescent suicidal behavior (Kashden et al. 1993; Kinsbury et al. 1999), even after controlling for hopelessness, neuroticism, external locus of control, and extroversion (Beautrais et al. 1999). Among adolescents, one type of poor impulse control, impulsive aggression (the tendency to react to frustration and/or provocation with aggression), is often prominent in disruptive behavior disorders, and has been shown to predict suicidal behavior (Apter et al. 1995; Beautrais et al.
