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Heritability of specific language impairment depends on diagnostic criteria
Article first published online: 17 SEP 2007
© 2007 The Authors
Genes, Brain and Behavior
Volume 7, Issue 3, pages 365–372, April 2008
How to Cite
Bishop, D. V. M. and Hayiou-Thomas, M. E. (2008), Heritability of specific language impairment depends on diagnostic criteria. Genes, Brain and Behavior, 7: 365–372. doi: 10.1111/j.1601-183X.2007.00360.x
- Issue published online: 17 SEP 2007
- Article first published online: 17 SEP 2007
- Received 15 July 2007, revised 11 September 2007, accepted for publication 12 September 2007
- specific language impairment;
Heritability estimates for specific language impairment (SLI) have been inconsistent. Four twin studies reported heritability of 0.5 or more, but a recent report from the Twins Early Development Study found negligible genetic influence in 4-year-olds. We considered whether the method of ascertainment influenced results and found substantially higher heritability if SLI was defined in terms of referral to speech and language pathology services than if defined by language test scores. Further analysis showed that presence of speech difficulties played a major role in determining whether a child had contact with services. Childhood language disorders that are identified by population screening are likely to have a different phenotype and different etiology from clinically referred cases. Genetic studies are more likely to find high heritability if they focus on cases who have speech difficulties and who have been referred for intervention.