The goal of the current review was to lay out the theoretical and empirical basis for considering impulsive delay discounting as an endophenotype for addictive disorders. Although it is only a recent area of focus, there is considerable evidence supporting this perspective. As a phenotype, impulsive discounting is stable over time, heritable, and robustly associated with addictive behavior. A small number of studies have identified direct associations between genetic variation and variation in discounting, and several preclinical studies have triangulated genetics, discounting, addiction liability, but these links remain considerably less well established. Moreover, caution is warranted in light of a history of highly promising initial findings that are ultimately false starts (or at least much more modest starts) in addiction genetics. This is particularly important because there are methodological issues pertaining to discounting as a phenotype that require careful consideration. Nonetheless, the existing literature provides strong basis for systematically investigating this hypothesis.
