Designing studies to investigate the relationships between genes, environments, and developmental language disorders

This paper focuses on designing studies that will compare children with developmental language disorders (DLD) drawn from several syndromes in which there are primary impairments in the acquisition of language. This kind of research can be used to address four key questions: (a) What are the developing language phenotypes that characterize specific disorders? (b) What factors are key precursors and predictors of language acquisition in DLD? (c) What are the genes that contribute to DLD in different syndromes? (d) What environmental factors influence the trajectories of language development in DLD? Several design issues are discussed including an overall study design, subject selection and recruitment, matching and comparisons across groups, and methodologies. A number of important challenges to the design and implementation of these kinds of studies are presented in the final section of the paper.