The examination of intermediate stages of problem alcohol use is critical to understanding how the contribution of genetics vs. environment shifts during the course of alcohol use, but only rarely have such studies been undertaken. Findings from among the few existing studies are somewhat inconsistent. Fowler et al.’s (2007) study of 11 to 19 year-olds reported that 41% of variance in the problem drinking indicator “getting into a situation you later regretted” was attributable to genetics, 16% to shared environment, whereas Rhee et al.’s (2003) study of adolescents in the same age range reported that 78% of variance in AUD symptoms was accounted for by genetics, none by shared environment. Another approach to elucidating the pathway from first use to problem use is to examine the overlap in genetic and environmental influences on the two phenotypes. The evidence suggests that approximately one third of the variance in AD is shared with variance in initiation (Fowler et al., 2007; Prescott and Kendler, 1999) and a recent study of Australian twins reported a correlation of 0.59 between the heritable factors influencing age
