Tambs K, Harris J R, Magnus P
Department of Epidemiology, National Institute of Public Health, Oslo, Norway.
Behav Genet. 1995 Jan;25(1):33-44. doi: 10.1007/BF02197240.
Two thousand five hundred seventy intact pairs and 724 single responders from Norwegian twins aged 18-25 years completed questionnaires with information about anxiety and depression and perceived cotwin closeness. The aim of the study was the univariate estimation of sex-specific genetic and environmental effects on an index tapping symptoms of anxiety and depression. An index of social closeness between cotwins was significantly related to the cotwin correlation for anxiety/depression scores. MZ pairs were reported to be closer than DZ pairs, and like-sexed DZ pairs were closer than unlike-sexed pairs. The symptom data were adjusted for this apparent violation of the "equal-environment" assumption in twin studies, but the adjustment did not dramatically affect the parameter estimates of genetic and environmental effects on anxiety/depression. A model specifying male (aM) and female (aF) genetic additive effects, shared environment for males (cM), and individual environmental effects (eM and eF) fitted the adjusted data very well. An alternative model, specifying aM = aF, cM = cF, and eM = eF, and no correlation between those environmental factors shared by brothers and those shared by sisters, fitted equally well. Estimated proportions of total variance from the first model were aM2 = .30, aF2 = .52, and cM2 = .21. The estimates from the second model were aM2 = aF2 = .43 and cM2 = cF2 = .11.
2570对完整的挪威18至25岁双胞胎及724名单独回应者完成了关于焦虑、抑郁以及感知到的双胞胎亲密程度的问卷调查。该研究的目的是对焦虑和抑郁症状指标进行性别特异性遗传和环境效应的单变量估计。双胞胎之间的社会亲密指数与焦虑/抑郁得分的双胞胎相关性显著相关。据报道，同卵双胞胎比异卵双胞胎更亲密，同性别的异卵双胞胎比不同性别的更亲密。针对双胞胎研究中这种明显违反“等环境”假设的情况，对症状数据进行了调整，但调整并未显著影响焦虑/抑郁的遗传和环境效应的参数估计。一个指定男性（aM）和女性（aF）遗传加性效应、男性共享环境（cM）以及个体环境效应（eM和eF）的模型很好地拟合了调整后的数据。另一个模型指定aM = aF、cM = cF、eM = eF，且兄弟共享的环境因素与姐妹共享的环境因素之间无相关性，拟合效果同样良好。第一个模型估计的总方差比例为aM2 = 0.30、aF2 = 0.52、cM2 = 0.21。第二个模型的估计值为aM2 = aF2 = 0.43、cM2 = cF2 = 0.11。
