Regarding the effect of the elder sibling combined alcohol problem index, for the drinking index measure, the AIC-determined best-fitting model included the hypothesized interaction between the elder sibling combined alcohol problem index and ALDH2 polymorphism (table S1, Model G). However, contrary to hypotheses, there was no evidence for moderation of ALDH2 effect by the elder sibling combined alcohol problem index upon the combined alcohol abuse and dependence symptom count, nor the diagnosis of alcohol abuse or dependence. Notably, for all three alcohol use outcomes, the magnitude of the positive relationship between the elder sibling combined alcohol problem index and the target sibling drinking index decreased over time. Similarly, we found no consistent evidence for interactions of ALDH2 with deviant peer behavior (table S2).
