total h2 of consumption in epochs 1 and 2 was higher than reported here, at about 0.20 for each time point. These estimates are based on quite small samples of early adolescents who drink, and the CIs are wide and span the estimates reported for the original coding scheme (95% CI 1.64×10−12 to 0.44 for epoch 1; 95% CI 6.38×10−12 to 0.40). Thus, while the true heritability of very early alcohol consumption might be underestimated in the current report, it is difficult to establish a precise estimate for this age range. Importantly, the overall structure of genetic influences is accurately captured by the original coding scheme.
