ABSTRACT
This chapter reviews current knowledge relating to the familial and genetic bases of speech and language disorders, and suggests possible relationships with Attention Deficit Hyperactivity Disorder (ADHD). It examines phenotypes and phenotype definitions, as well as incidence and prevalence of speech and language disorders. Developmental speech and language difficulties in children include a heterogeneous group of disorders that affect speech sound production, as well as receptive and expressive language skills. Traditional classification systems divide disorders into those of articulation/phonology; disorders affecting the speech sound system; language disorders including difficulties with syntax, semantics, or pragmatics; disorders of fluency including stuttering and prosody disturbances; and voice disorders. Identification of affected family members presents another challenge to genetic studies in the field. The heterogeneous nature of speech and language disorders suggests that several different underlying genetic aetiologies may be involved.
