Joseph Jay
La Familia Counseling Service, Hayward, California, USA.
Psychiatr Q. 2002 Spring;73(1):71-82. doi: 10.1023/a:1012896802713.
Twin studies are frequently cited in support of the influence of genetic factors for a wide range of psychiatric conditions and psychological trait differences. The most common method, known as the classical twin method, compares the concordance rates or correlations of reared-together identical (MZ) vs. reared-together same-sex fraternal (DZ) twins. However, drawing genetic inferences from MZ-DZ comparisons is problematic due to methodological problems and questionable assumptions. It is argued that the main theoretical assumption of the twin method--known as the "equal environment assumption"--is not tenable. The twin method is therefore of doubtful value as an indicator of genetic influences. Studies of reared-apart twins are discussed, and it is noted that these studies are also vulnerable to methodological problems and environmental confounds. It is concluded that there is little reason to believe that twin studies provide evidence in favor of genetic influences on psychiatric disorders and human behavioral differences.
双胞胎研究经常被引用来支持遗传因素对广泛的精神疾病和心理特质差异的影响。最常见的方法，即经典双胞胎法，比较一起抚养的同卵双胞胎（MZ）与一起抚养的同性异卵双胞胎（DZ）的一致率或相关性。然而，由于方法学问题和可疑的假设，从MZ-DZ比较中得出遗传推断存在问题。有人认为，双胞胎法的主要理论假设——即“同等环境假设”——是站不住脚的。因此，作为遗传影响的指标，双胞胎法的价值值得怀疑。文中讨论了分开抚养的双胞胎的研究，并指出这些研究也容易受到方法学问题和环境混杂因素的影响。得出的结论是，几乎没有理由相信双胞胎研究能提供证据支持遗传因素对精神疾病和人类行为差异有影响。
