Familial concentration of developmental language impairment.

A questionnaire concerning the history of treatment of developmental language disorder was used to evaluate the prevalence of these problems within the immediate family members of second-grade children with and without language impairment. The data obtained from these families revealed strong evidence that such language problems are not randomly distributed across families but rather tend to concentrate within families. Although all family members of the language-impaired second graders demonstrated substantially increased odds for language impairment over those who came from families with normal second graders, a considerable range of increased odds for language impairment existed among the family members. Specifically, brothers and to a lesser degree sisters had a higher familial association with language impairment than did the parents. These results suggest that the factors that contribute to developmental language disorders are at least in part associated with the family unit.