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Common Genetic Influences for ADHD and Reading Disability

  • Synopsis: Published: 2010-12-08 - Attention Deficit Hyperactivity Disorder (ADHD) and developmental reading disability (RD) are complex childhood disorders that frequently occur together. For further information pertaining to this article contact: Elsevier.

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A new twin-study has found that their co-occurrence may be linked to slow processing speed.

Attention Deficit Hyperactivity Disorder (ADHD) and developmental reading disability (RD) are complex childhood disorders that frequently occur together; if a child is experiencing trouble with reading, symptoms of ADHD are often also present. However, the reason for this correlation remains unknown. A new study reported in the latest special issue of Cortex (www.sciencedirect.com/science/journal/00109452), dedicated to "Developmental Dyslexia and Dysgraphia", has suggested that the disorders have common genetic influences, which may also lead to slow processing speed - the brain taking longer to make sense of the information it receives.

The researchers looked at 457 pairs of twins from the Colorado Learning Disabilities Research Center (CLDRC) twin study - an ongoing study of the causes of reading disabilities, ADHD, and related disorders. Dr Erik Willcutt and colleagues compared groups of participants with and without RD and ADHD, using a variety of tests to measure general cognitive ability, processing speed, reading and language skills, and then analyzed results from pairs of twins within those groups to determine the genetic causes of any correlations. The use of identical twins, who share all their genes, and non-identical twins, who share only half their genes, allowed the researchers to distinguish between genetic and environmental influences on the participants' cognitive abilities.

The findings showed that both RD and ADHD are complex disorders, influenced by many factors; ADHD on its own was associated with a reduced ability to inhibit responses to stimuli, while reading disabilities were associated with various weaknesses in language and memory. However, both disorders were associated with a slow processing speed and the twin-analyses further revealed a significant genetic correlation between RD and ADHD, i.e., a participant with one of the disorders was more likely to show symptoms of the other. The authors of the study suggest that processing efficiency may therefore be a useful marker to look for in future studies of the connection between the two disorders.

About Cortex - Cortex is an international journal devoted to the study of cognition and of the relationship between the nervous system and mental processes, particularly as these are reflected in the behavior of patients with acquired brain lesions, normal volunteers, children with typical and atypical development, and in the activation of brain regions and systems as recorded by functional neuroimaging techniques. It was founded in 1964 by Ennio De Renzi. The Editor in-chief of Cortex is Sergio Della Sala, Professor of Human Cognitive Neuroscience at the University of Edinburgh. Fax: 0131 6513230, e-mail: cortex@ed.ac.uk. Cortex is available online at www.sciencedirect.com/science/journal/00109452

About Elsevier - Elsevier is a world-leading publisher of scientific, technical and medical information products and services. The company works in partnership with the global science and health communities to publish more than 2,000 journals, including the Lancet (www.thelancet.com) and Cell (www.cell.com), and close to 20,000 book titles, including major reference works from Mosby and Saunders. Elsevier's online solutions include ScienceDirect (www.sciencedirect.com), Scopus (www.scopus.com), Reaxys (www.reaxys.com), MD Consult (www.mdconsult.com) and Nursing Consult (www.nursingconsult.com), which enhance the productivity of science and health professionals, and the SciVal suite (www.scival.com) and MEDai's Pinpoint Review (www.medai.com), which help research and health care institutions deliver better outcomes more cost-effectively.

A global business headquartered in Amsterdam, Elsevier (www.elsevier.com) employs 7,000 people worldwide. The company is part of Reed Elsevier Group PLC (www.reedelsevier.com), a world-leading publisher and information provider. The ticker symbols are REN (Euronext Amsterdam), REL (London Stock Exchange), RUK and ENL (New York Stock Exchange).



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