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Evidence for shared genetic risk between ADHD symptoms and reduced mathematics ability: a twin study

Authors

  • Corina U. Greven,

    Corresponding author
    1. Radboud University Medical Centre Nijmegen, Donders Institute for Brain, Cognition and Behaviour, Department of Cognitive Neuroscience, Nijmegen, The Netherlands
    2. King's College London, MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, London, UK
    • Correspondence

      Corina U. Greven, Radboud University Medical Centre Nijmegen, Donders Institute for Brain, Cognition and Behaviour, Department of Cognitive Neuroscience, internal post 204, Nijmegen, The Netherlands; Email:corina.greven@donders.ru.nl

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  • Yulia Kovas,

    1. King's College London, MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, London, UK
    2. Department of Psychology, Tomsk State University, Tomsk, Russia
    3. Department of Psychology, Goldsmiths College, University of London, London, UK
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  • Erik G. Willcutt,

    1. Department of Psychology and Neuroscience, University of Colorado, Boulder, CO, USA
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  • Stephen A. Petrill,

    1. Department of Human Development and Family Science, Ohio State University, Columbus, OH, USA
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  • Robert Plomin

    1. King's College London, MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, London, UK
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  • Conflicts of interest statement: No conflicts declared.
  • There is no gold-standard, universally applied definition of mathematics disability, and the literature is additionally complicated by the use of inconsistent labels (e.g., mathematics difficulties/underachievement/disability/disorder, developmental dyscalculia, reduced mathematics ability/skill), some of which differ conceptually. For the literature reviewed in this paper, we make no differentiation between these labels and concepts. However, for the data shown in this paper, we consider the term ‘mathematics ability’ to refer to a normally distributed complex trait that ranges from low (disability) to high (ability).

Abstract

Background

Attention-deficit/hyperactivity disorder (ADHD) symptoms and mathematics ability are associated, but little is known about the genetic and environmental influences underlying this association.

Methods

Data came from more than 6,000 twelve-year-old twin pairs from the UK population-representative Twins Early Development Study. Parents rated each twin's behaviour using a DSM-IV-based 18-item questionnaire of inattentive and hyperactive–impulsive ADHD symptoms. Mathematics tests based on the UK National Curriculum were completed by each twin. The twins also completed standardised tests of reading and general cognitive ability. Multivariate twin model fitting was applied.

Results

Inattentive and hyperactive–impulsive ADHD symptoms were highly heritable (67% and 73% respectively). Mathematics ability was moderately heritable (46%). Mathematics ability and inattentiveness showed a significantly greater phenotypic correlation (rp = −.26) and genetic correlation (rA = −.41) than mathematics ability and hyperactivity–impulsivity (rp = −.18; rA = −.22). The genetic correlation between inattentiveness and mathematics ability was largely independent from hyperactivity-impulsivity, and was only partially accounted for by genetic influences related to reading and general cognitive ability.

Conclusions

Results revealed the novel finding that mathematics ability shows significantly stronger phenotypic and genetic associations with inattentiveness than with hyperactivity–impulsivity. Genetic associations between inattentiveness and mathematics ability could only partially be accounted for by hyperactivity–impulsivity, reading and general cognitive ability. Results suggest that mathematics ability is associated with ADHD symptoms largely because it shares genetic risk factors with inattentiveness, and provide further evidence for considering inattentiveness and hyperactivity–impulsivity separately. DNA markers for ADHD symptoms (especially inattentiveness) may also be candidate risk factors for mathematics ability and vice versa.

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