sibling pair, as well as all adopted youth. Ideally, this would provide an estimate of the aggregate effect of common SNPs in the offspring youth sample and would be comparable to that produced by the unrelated parent sample. (3) We conducted the same analysis on the full sample of youth offspring (n = 3336), without concern for genetic relatedness. Because this analysis confounds phenotypes, genotypes, and shared environment, it should return a genetic random effect approximate to the sum of genetic and shared environment from the biometric analysis (i.e., approximately A + C). (4) Finally, we estimate the random genetic effect in the full sample (N = 7188), which should provide an estimate of the random effect somewhere between the unrelated sample and the youth offspring sample, as the full sample has less of a shared environment confound than the twin sample. That is, parents are phenotypically related due to shared environment, but the extent of shared environmental influence is less than that between twins, again under the simplifying assumption of no assortative mating.
