The finding that impulsivity was highly related to externalizing behaviors was expected since such problems are characterized by deficits in impulse control (Gottfredson & Hirschi, 1990; Waschbusch, 2002; Waschbusch et al., 2002). We were surprised however to find that externalizing behaviors did not correlate with risk behavior once impulsivity was controlled. Tarter’s neurobehavioral disinhibition model explicitly predicts such an association (Tarter et al., 2004; Tarter et al., 2003). Furthermore, longitudinal studies find that early evidence of conduct disorder and other externalizing behaviors is related to later drug use and fighting (Zucker, 2006). However, impulsivity may be the central predisposing condition underlying both early manifestations of conduct disorder and later health-risk behavior. Studies that examine very early temperamental factors find that behaviors symptomatic of poor behavior control predict later externalizing problems (Caspi et al., 1995; White et al., 1994), suggesting that impulsivity is an important factor in the development of such outcomes. Our results support this conclusion, although a potential additional link between externalizing behavior and risk behavior cannot be ruled out given the presence of some, albeit statistically non-significant, relation that remains.
