The results reported here should be considered in the context of several limitations. Data were only available for white men, and the generalizability of these results to women and other ethnicities is not clear. Additionally, alcohol consumption was reported retrospectively, raising the possibility of errors in recall. We were unable to examine changes in A, C and E influences beyond the early 30 s; examination of later age ranges would have resulted in abundant missing data as fewer members of the sample had reached later ages. Finally, we opted to retain shared environmental influences in the model based on theoretical and previous empirical evidence of their relevance to early drinking behaviors; however, this resulted in a final model that was less parsimonious than was possible. These findings warrant replication in a sample of twins that is prospectively assessed and includes both genders and other ethnicities, if possible.
