Biological Psychiatry
Volume 62, Issue 9 , Pages 991-998, 1 November 2007

Testing for Neuropsychological Endophenotypes in Siblings Discordant for Attention-Deficit/Hyperactivity Disorder

  • L. Cinnamon Bidwell

      Affiliations

    • Department of Psychology, University of Colorado, Boulder, Colorado
    • Institute for Behavioral Genetics, University of Colorado, Boulder, Colorado
    • Corresponding Author InformationAddress reprint requests to L. Cinnamon Bidwell, M.A., UCB 345, Boulder, CO 80301
    • ,
  • Erik G. Willcutt

      Affiliations

    • Department of Psychology, University of Colorado, Boulder, Colorado
    • Institute for Behavioral Genetics, University of Colorado, Boulder, Colorado
    • ,
  • John C. DeFries

      Affiliations

    • Department of Psychology, University of Colorado, Boulder, Colorado
    • Institute for Behavioral Genetics, University of Colorado, Boulder, Colorado
    • ,
  • Bruce F. Pennington

      Affiliations

    • Institute for Behavioral Genetics, University of Colorado, Boulder, Colorado
    • Department of Psychology, University of Denver, Colorado.

Received 5 December 2006; received in revised form 3 April 2007; accepted 4 April 2007. published online 25 June 2007.

Background

Neurocognitive deficits associated with attention-deficit/hyperactivity disorder (ADHD) might be useful intermediate endophenotypes for determining specific genetic pathways that contribute to ADHD.

Methods

This study administered 17 measures from prominent neuropsychological theories of ADHD (executive function, processing speed, arousal regulation and, motivation/delay aversion) in dizygotic (DZ) twin pairs discordant for ADHD and control twin pairs (ages 8–18 years) to compare performance between twins affected with ADHD (n = 266), their unaffected co-twins (n = 228), and control children from twin pairs without ADHD or learning difficulties (n = 332).

Results

The ADHD subjects show significant impairment on executive function, processing speed, and response variability measures compared with control subjects. Unaffected co-twins of ADHD subjects are significantly impaired on nearly all the same measures as their ADHD siblings, even when subclinical symptoms of ADHD are controlled.

Conclusions

Executive function, processing speed, and response variability deficits might be useful endophenotypes for genetic studies of ADHD.

Key Words: ADHD, endophenotype, executive function, genetics, neuropsychology, processing speed

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PII: S0006-3223(07)00325-3

doi:10.1016/j.biopsych.2007.04.003

Biological Psychiatry
Volume 62, Issue 9 , Pages 991-998, 1 November 2007

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