An understanding of biological mechanisms underlying the relationship between impulsivity and initiation of alcohol use also depends on careful selection and description of the behaviors under study. We reviewed two studies demonstrating relationships between impulsivity and family history of alcoholism; Petry et al. (2002) focused on delay discounting impulsivity, whereas Hill and colleagues (2009) focused on self-control aspects of impulsivity. It would be of great interest to examine self-control in a design such as that used by Petry et al. and to examine discounting in the design used by Hill et al. In sum, future studies will be enriched by inclusion of a range of measures, addressing more than a single dimension of the complex construct of impulsivity, including a clear strategy for differentiation and causal directions encompassing biological evidence.
