Genetic and Environmental Mediation of the Relationship Between Language and Nonverbal Impairment in 4-Year-Old Twins This study of 4-year-old twins investigated the genetic and environmental origins of comorbidity between language impairment and nonverbal ability by testing the extent to which language impairment in one twin predicted nonverbal ability in the co-twin. Impairment of language ability was defined as scores below the 15th percentile on a ... Research Article
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Research Article  |   December 01, 2003
Genetic and Environmental Mediation of the Relationship Between Language and Nonverbal Impairment in 4-Year-Old Twins
 
Author Affiliations & Notes
  • Essi Viding
    Institute of Psychiatry, London
  • Thomas S. Price
    Institute of Psychiatry, London
  • Frank M. Spinath
    Institute of Psychiatry, London
  • Dorothy V. M. Bishop
    University of Oxford, Oxford, England
  • Philip S. Dale
    University of Missouri-Columbia
  • Robert Plomin
    Institute of Psychiatry, London
  • Contact author: Essi Viding, Social Genetic and Developmental Psychiatry Centre, Box Number P080, Institute of Psychiatry, De Crespigny Park, London SE5 8AF, England. E-mail: spjgemc@iop.kcl.ac.uk
  • Currently at the Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, England.
    Currently at the Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, England.×
  • Currently at the University of Bielefeld, Bielefeld, Germany.
    Currently at the University of Bielefeld, Bielefeld, Germany.×
Article Information
Special Populations / Genetic & Congenital Disorders / Language Disorders / Language / Research Articles
Research Article   |   December 01, 2003
Genetic and Environmental Mediation of the Relationship Between Language and Nonverbal Impairment in 4-Year-Old Twins
Journal of Speech, Language, and Hearing Research, December 2003, Vol. 46, 1271-1282. doi:10.1044/1092-4388(2003/099)
History: Received September 19, 2002 , Accepted March 25, 2003
 
Journal of Speech, Language, and Hearing Research, December 2003, Vol. 46, 1271-1282. doi:10.1044/1092-4388(2003/099)
History: Received September 19, 2002; Accepted March 25, 2003
Web of Science® Times Cited: 26

This study of 4-year-old twins investigated the genetic and environmental origins of comorbidity between language impairment and nonverbal ability by testing the extent to which language impairment in one twin predicted nonverbal ability in the co-twin. Impairment of language ability was defined as scores below the 15th percentile on a general language scale derived from a battery of diverse language tests. Four hundred thirty-six children, members of 160 monozygotic (MZ) and 131 same-sex dizygotic (DZ) twin pairs, were identified as language impaired. Language-impaired probands also suffered significant impairments in nonverbal ability. DeFries-Fulker extremes analysis showed evidence for substantial genetic mediation of the phenotypic relationship between language impairment and poor nonverbal ability in that language problems in one twin predicted poor nonverbal ability in the co-twin, much more so for MZ twins than for DZ twins. This finding held even when we excluded those children with language impairment whose nonverbal score indicated general cognitive delay. These results point to a general genetic factor that includes both language and nonverbal problems.

Acknowledgments
We are indebted to the parents of the twins in the Twins Early Development Study (TEDS) for making the study possible. The TEDS is supported by a programme grant from the U.K. Medical Research Council.
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