The findings from these studies modestly implicate discounting as a mechanism conferring the risk from family history, but significant methodological issues make this conclusion far from definitive. For example, two of the three preceding studies had very small samples that were underpowered for effects below relatively large magnitude group differences. Moreover, these studies focused specifically on family history of alcohol misuse, but have not necessarily ruled out the presence of other drug misuse or other forms of addictive behavior in the FH− samples. This is a problem because, as noted above, impulsive discounting is associated with an array of addictive disorders (MacKillop et al., 2011) and the ostensible ‘control group’ may have been contaminated with individuals who also had a family history of addictive behavior, substantially undermining the experimental comparison. Most recently, in the largest study to date (N = 298), some of these considerations were addressed via careful characterization of family history status for alcohol and other drugs, and also quantification of the density of the family history (Acheson, Vincent, Sorocco, & Lovallo, 2011). In this study, FH+ status
