While a standard part of twin modeling, the magnitude of shared environment (c2) is rarely examined by comparing estimates obtained using other methods. To clarify these effects on familial resemblance, we estimated c2 for 20 diverse phenotypes in: (i) monozygotic and dizygotic twins, (ii) all step-siblings, and (iii) reared together and apart half-siblings, ascertained from the Swedish general population. The mean c2 estimates (± 95% CIs) differed across methods and were higher from twins (0.18; 0.13-0.23) than from the step (0.12; 0.09-0.14) and half-sibs (0.09; 0.06-0.13). c2 estimates correlated moderately across these three methods (ICC = + 0.28). When step-siblings from blended (each sib biologically related to one parent) and adoption-like families (one sib offspring of both parents and one of neither), were examined separately, resemblance was much lower in the latter. We need to clarify the range of environmental processes now considered together under the term "shared environment."

中文翻译：

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共享环境的本质。

虽然共享环境 (c2) 的大小是双胞胎建模的标准部分，但很少通过比较使用其他方法获得的估计值来检查。为了阐明这些对家族相似性的影响，我们估计了 20 种不同表型的 c2：（i）同卵双胞胎和异卵双胞胎，（ii）所有继兄弟姐妹，以及（iii）共同抚养或分开抚养的同父异母兄弟姐妹，由瑞典将军确定人口。不同方法的平均 c2 估计值 (± 95% CI) 不同，双胞胎 (0.18; 0.13-0.23) 高于同级 (0.12; 0.09-0.14) 和半同胞 (0.09; 0.06-0.13)。c2 估计值在这三种方法中具有中等相关性 (ICC = + 0.28)。当分别检查混血家庭（每个兄弟姐妹与父母之一有生物学关系）和收养类家庭（父母双方都有一个兄弟姐妹的后代，或者两者都不是）的继兄弟姐妹时，后者的相似性要低得多。我们需要澄清现在在“共享环境”一词下一起考虑的环境过程的范围。