Department of Epidemiology, School of Public Health, Aarhus University, Aarhus C, Aarhus, Denmark.
Eur Child Adolesc Psychiatry. 2012 Sep;21(9):503-9. doi: 10.1007/s00787-012-0287-4. Epub 2012 May 29.
It has been hypothesized that prenatal exposure to testosterone may be associated with traits of attention-deficit/hyperactivity disorder (ADHD) or autism spectrum disorder (ASD). We conducted a population-based study of dizygotic female twins to elucidate this hypothesis, assuming that the sex of the co-twin influences the level of prenatal exposure to testosterone. We invited parents of 24,552 3- to 15-year-old twins to answer questionnaires on traits of ADHD and ASD. We analysed the data using a proportional odds model with sex of the co-twin as an instrumental variable for prenatal exposure to testosterone of female twins. We received responses for 6,339 girls from dizygotic twin pairs. Odds ratios for male versus female co-twin were 0.71 (95 % confidence interval 0.61-0.81) for ADHD traits and 0.74 (0.66-0.83) for ASD traits, indicating that a twin brother reduces traits of ADHD and ASD in females. In conclusion, we found that female twins with a twin brother scored significantly lower in parent-reported traits of ADHD and ASD than those with a twin sister. The reason for this may be parental reporting bias, or confounding by unmeasured variables, or a causal effect of an intrauterine environment modified by the sex of the co-twin in the opposite direction of what we expected.
有人假设，胎儿期暴露于睾酮可能与注意力缺陷多动障碍（ADHD）或自闭症谱系障碍（ASD）的特征有关。我们对双卵双胞胎的女性进行了一项基于人群的研究，以阐明这一假设，即双胞胎的性别会影响胎儿期暴露于睾酮的水平。我们邀请了 24552 对 3 至 15 岁双胞胎的父母回答有关 ADHD 和 ASD 特征的问卷。我们使用双生子的性别作为女性双生子胎儿期暴露于睾酮的工具变量，在比例优势模型中分析了数据。我们收到了 6339 名来自双卵双胞胎的女孩的答复。对于 ADHD 特征，男性与女性同卵双胞胎相比的优势比为 0.71（95%置信区间 0.61-0.81），对于 ASD 特征为 0.74（0.66-0.83），这表明双胞胎兄弟会降低女性的 ADHD 和 ASD 特征。总之，我们发现，有双胞胎兄弟的女性双胞胎在父母报告的 ADHD 和 ASD 特征上的得分明显低于有双胞胎姐妹的女性双胞胎。其原因可能是父母报告的偏差，或未测量变量的混杂，或由同卵双胞胎的性别在与我们预期相反的方向上改变的宫内环境引起的因果效应。
