The first goal of this study was to examine developmentally the impact of two different classes of genetic risk factors on alcohol consumption: those specific to risk for AUDs and those reflecting a more general liability to externalizing disorders. We found a temporal progression in their effects. The non-specific genetic risk factors rose rapidly in importance in early to mid-adolescence, peaking in influence at ages 15–17 and then declining gradually in impact from late adolescence onward. By contrast, the alcohol-specific risk factors did not have maximal impact on alcohol consumption until ages 30–33. These results suggest that, in early adolescence, genetic influences on alcohol intake are preponderantly non-specific and may reflect a more general picture of largely adolescent-limited externalizing behaviors (Moffitt, 1993; Moffitt et al. 2002). However, the specific genetic risk factors become more important than non-specific influences in early to mid-adulthood, a typical time for the onset of serious alcohol problems (Schuckit et al. 1995). These results provide a good example of genetic and developmental equifinality (Cicchetti & Rogosch, 1996) in which the same phenotype at different developmental stages can be influenced by different combinations of distinct genetic risk factors.
