The preceding sections provide the theoretical and empirical basis for pursuing delay discounting as an endophenotype for addictive disorders. This is clearly a promising area of research and success could have a major impact in terms of understanding the genetic basis of addiction, the nature of impulsivity, and even prevention and treatment. Importantly, however, there are a number of considerations and challenges that pertain to delay discounting in general, but especially genetic research. To start, there are issues of measurement with regard to discounting, as a wide array of assessments are used in the field (MacKillop et al., 2011) and the discounting indices vary in terms of how well they correlate with each other, ranging from very high magnitude to negligible correlations (e.g., Epstein et al., 2003; Krishnan-Sarin et al., 2007; MacKillop et al., 2010; Paloyelis et al., 2010). This may seem surprising at first glance, but when the diversity of commodities, delay durations, and size of commodity are considered, these variable relationships make more sense. As such, it will be critical for investigators to use consistent assessments across investigations
