Another common methodology for investigating endophenotypes is examining whether the phenotype of interest aggregates in individuals who do not themselves have the disorder, but have a family history (FH) of the condition. This permits assessing the presence of the endophenotype in unaffected but nonetheless at-risk relatives. For heritable disorders, like addictive disorders, the presence of a FH increases risk for the condition and, if FH status is associated with a specific characteristic, it implicates the characteristic as a potential mechanism. To date, only a small number of studies have been conducted using this approach with discounting and the findings have been mixed. Petry, Kirby, and Kranzler (2002) examined paternal alcohol dependence family history status in 122 adults and found significantly more impulsive discounting in FH+ women, but not men. Crean, Richards, and de Wit (2002) also examined paternal alcoholism in the context of a tryptophan depletion laboratory challenge, but found no differences between the two groups and no effect of the manipulation on discounting. In a relatively small sample (N = 33), Herting, Schwartz, Mitchell, and Nagel (2010) detected greater
