Developmental Language Disorders: From Phenotypes to Etiologies

Developmental language disorders almost certainly are influenced by both genetic and environmental factors. Sameroff and colleagues (e.g., Sameroff & Fiese, 2000) have argued for years that genotype, phenotype, and “environtype” interact over time in reciprocal and mutually influential transactions to shape developmental outcomes for children and adults. Understanding the relative contributions of each and discovering the mechanisms and directions of influence are goals that lie at the heart of understanding developmental phenomena, including developmental language disorders, and ultimately could lead to new insights into the nature and timing of events or experiences most likely to influence developmental outcomes (Reiss & Neiderhiser, 2000).

Many approaches can be used to study how genes, environments, and developmental language disorders (DLDs) interact. Historically, this research has been complicated by the lack of data documenting specific genetic causes of DLDs. Although recent research provides strong evidence for a genetic component of developmental disorders such as autism (Cook, 1998) and specific reading disability (DeFries & Alarcon, 1996), the identification of specific genes and an understanding of the biological mechanisms by which they influence language development are still unknown.

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