Greven Corina U, Merwood Andrew, van der Meer Jolanda M J, Haworth Claire M A, Rommelse Nanda, Buitelaar Jan K
Department of Cognitive Neuroscience, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands.
Karakter Child and Adolescent Psychiatry University Center, Nijmegen, The Netherlands.
J Child Psychol Psychiatry. 2016 Apr;57(4):523-31. doi: 10.1111/jcpp.12475. Epub 2015 Oct 17.
Although attention deficit hyperactivity disorder (ADHD) is thought to reflect a continuously distributed quantitative trait, it is assessed through binary diagnosis or skewed measures biased towards its high, symptomatic extreme. A growing trend is to study the positive tail of normally distributed traits, a promising avenue, for example, to study high intelligence to increase power for gene-hunting for intelligence. However, the emergence of such a 'positive genetics' model has been tempered for ADHD due to poor phenotypic resolution at the low extreme. Overcoming this methodological limitation, we conduct the first study to assess the aetiologies of low extreme ADHD traits.
In a population-representative sample of 2,143 twins, the Strength and Weaknesses of ADHD Symptoms and Normal behaviour (SWAN) questionnaire was used to assess ADHD traits on a continuum from low to high. Aetiological influences on extreme ADHD traits were estimated using DeFries-Fulker extremes analysis. ADHD traits were related to behavioural, cognitive and home environmental outcomes using regression.
Low extreme ADHD traits were significantly influenced by shared environmental factors (23-35%) but were not significantly heritable. In contrast, high-extreme ADHD traits showed significant heritability (39-51%) but no shared environmental influences. Compared to individuals with high extreme or with average levels of ADHD traits, individuals with low extreme ADHD traits showed fewer internalizing and externalizing behaviour problems, better cognitive performance and more positive behaviours and positive home environmental outcomes.
Shared environmental influences on low extreme ADHD traits may reflect passive gene-environment correlation, which arises because parents provide environments as well as passing on genes. Studying the low extreme opens new avenues to study mechanisms underlying previously neglected positive behaviours. This is different from the current deficit-based model of intervention, but congruent with a population-level approach to improving youth wellbeing.
尽管注意力缺陷多动障碍（ADHD）被认为反映的是一种连续分布的数量性状，但它是通过二元诊断或偏向于其高症状极端的偏态测量方法来评估的。研究正态分布性状的正向尾部是一种日益增长的趋势，这是一条很有前景的途径，例如，研究高智商以提高寻找智力相关基因的效力。然而，由于在低极端情况下表型分辨率较差，这种“正向遗传学”模型在ADHD研究中受到了限制。为克服这一方法学上的局限性，我们开展了第一项评估低极端ADHD性状病因的研究。
在一个具有人群代表性的2143对双胞胎样本中，使用ADHD症状与正常行为的优势与劣势（SWAN）问卷来评估从低到高连续变化的ADHD性状。使用德弗里斯 - 富尔克极端分析来估计对极端ADHD性状的病因影响。通过回归分析将ADHD性状与行为、认知和家庭环境结果相关联。
低极端ADHD性状受到共享环境因素的显著影响（23 - 35%），但遗传度不显著。相比之下，高极端ADHD性状显示出显著的遗传度（39 - 51%），但没有共享环境影响。与具有高极端或平均ADHD性状水平的个体相比，具有低极端ADHD性状的个体表现出较少的内化和外化行为问题、更好的认知表现以及更积极的行为和更积极的家庭环境结果。
共享环境对低极端ADHD性状的影响可能反映了被动基因 - 环境相关性，这是因为父母既传递基因也提供环境。研究低极端情况为研究先前被忽视的积极行为背后的机制开辟了新途径。这与当前基于缺陷的干预模型不同，但与改善青少年幸福感的人群水平方法相一致。
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