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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.

Original publication

DOI

10.1111/j.1601-183X.2007.00360.x

Type

Journal article

Journal

Genes Brain Behav

Publication Date

04/2008

Volume

7

Pages

365 - 372

Keywords

Aging, Child, Child, Preschool, Cognition, Diagnosis, Differential, Female, Humans, Language Disorders, Longitudinal Studies, Male, Phenotype, Speech Disorders, Surveys and Questionnaires