There is substantial consistency in the estimates of genetic and shared environmental variance in liability to AUD. In particular, we found no significant differences between the estimates derived from twin studies and adoption studies, from studies relying on personal interviews v. official records for the assessment of AUD or from studies of males v. females. Furthermore by including a large number of studies into the analysis, we were able to detect significant shared environmental effects that account for ~10% of the variance in AUD. These findings should enhance our confidence in the validity of our heritability estimates for AUD and provide a firm footing for efforts now well underway to try to localize on the human genome the specific genetic variants that contribute to the genetic risk for AUD.
