What parallels can be drawn between our results and the extensive rodent literature on genetic influences on alcohol-related traits?41,42 It is difficult to determine definitively how many of the DSM-IV AD criteria can be meaningfully measured in rodents. As some (for example, ‘a persistent desire … to cut down’) clearly cannot,43 two DSM-IV AD criteria—tolerance and withdrawal—can be evaluated in rodents using methods broadly congruent with the human phenotypes.43,44 An examination of Figure 1 would lead to the prediction that if rodents are like humans, the relationship between genetic risk factors for tolerance and withdrawal should be modest and positive. As the two criteria do not load strongly on the same common factor, they both have positive loadings on all three factors.
