Autism spectrum condition and attention-deficit/hyperactivity disorder (ADHD) are associated with a range of physical health conditions. The aim of this study was to examine the etiological components contributing to co-occurring physical health conditions in autism and ADHD. In this nationwide Child and Adolescent Twin Study in Sweden, we analyzed data from 10,347 twin pairs aged 9 and 12. Clinical diagnoses of autism, ADHD, and physical health conditions were identified through the Swedish National Patient Register. Subclinical phenotypes of autism and ADHD were defined by symptom thresholds on a standardized parent-interview, the Autism–Tics, ADHD, and Other Comorbidities inventory. Associations between physical health conditions and autism/ADHD phenotypes were examined using generalized estimating equations. Bivariate twin models were applied to estimate the extent to which genetic and environmental risk factors accounted for physical health comorbidities. Similar patterns of association with physical health conditions were found in clinical and subclinical autism/ADHD, with odds ratios ranging from 1.31 for asthma in subclinical ADHD to 8.03 for epilepsy in clinical autism. The estimated genetic correlation (ra) with epilepsy was 0.50 for clinical autism and 0.35 for subclinical autism. In addition, a modest genetic correlation was estimated between clinical autism and constipation (ra = 0.31), functional diarrhea (ra = 0.27) as well as mixed gastrointestinal disorders (ra = 0.30). Genetic effects contributed 0.86 for mixed gastrointestinal disorders in clinical ADHD (ra = 0.21). Finally, subclinical ADHD shared genetic risk factors with epilepsy, constipation, and mixed gastrointestinal disorders (ra = 0.30, 0.17, and 0.17, respectively). Importantly, since medical records from primary care were not included in the registry data used, we probably identified only more severe rather than the full range of physical health conditions. Furthermore, it needs to be considered that the higher prevalence of physical health conditions among autistic children and children with ADHD could be associated with the increased number of medical visits. Shared genetic effects contribute significantly to autism and ADHD phenotypes with the co-occurring physical health conditions across different organ systems, including epilepsy and gastrointestinal disorders. The shared genetic liability with co-occurring physical health conditions was present across different levels of autism and ADHD symptom severity.

中文翻译：

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遗传和环境对自闭症谱系疾病和注意力缺陷/多动障碍中同时发生的身体健康状况的贡献

自闭症谱系疾病和注意力缺陷/多动障碍 (ADHD) 与一系列身体健康状况有关。本研究的目的是检查导致自闭症和多动症同时发生的身体健康状况的病因学成分。在这项瑞典全国儿童和青少年双胞胎研究中，我们分析了来自 10,347 对年龄分别为 9 岁和 12 岁的双胞胎的数据。自闭症、多动症和身体健康状况的临床诊断是通过瑞典国家患者登记册确定的。自闭症和 ADHD 的亚临床表型由标准化家长访谈、自闭症抽动症、ADHD 和其他合并症量表的症状阈值定义。使用广义估计方程检查身体健康状况与自闭症/多动症表型之间的关联。应用双变量双胞胎模型来估计遗传和环境风险因素对身体健康合并症的影响程度。在临床和亚临床自闭症/ADHD 中发现了与身体健康状况相似的关联模式，比值比从亚临床 ADHD 哮喘的 1.31 到临床自闭症癫痫的 8.03。临床自闭症与癫痫的估计遗传相关性 (ra) 为 0.50，亚临床自闭症为 0.35。此外，估计临床自闭症与便秘 (ra = 0.31)、功能性腹泻 (ra = 0.27) 以及混合性胃肠道疾病 (ra = 0.30) 之间存在适度的遗传相关性。遗传效应对临床 ADHD 中的混合性胃肠道疾病的贡献为 0.86 (ra = 0.21)。最后，亚临床 ADHD 与癫痫有共同的遗传危险因素，便秘和混合性胃肠道疾病（分别为 ra = 0.30、0.17 和 0.17）。重要的是，由于来自初级保健的医疗记录未包含在所使用的登记数据中，我们可能只确定了更严重的而不是全部的身体健康状况。此外，需要考虑的是，自闭症儿童和多动症儿童身体健康状况的患病率较高可能与就诊次数的增加有关。共同的遗传效应对自闭症和 ADHD 表型有显着影响，同时在不同器官系统（包括癫痫和胃肠道疾病）中同时发生身体健康状况。不同程度的自闭症和 ADHD 症状严重程度都存在与共同发生的身体健康状况相关的遗传责任。