The Twins Early Development Study (TEDS) focuses on the early development of the three most common psychological problems in childhood: communication disorders, mild mental impairment and behavior problems. The TEDS twins were assessed longitudinally at 2, 3, 4 and 7 years of age in order to investigate genetic and environmental contributions to change and continuity in language and cognitive development; it is multivariate in order to examine the origins of comorbidity; and it uses a large sample in order to study abnormal development in the context of normal development. The twins were identified from birth records of twins born in the UK in 1994-96. More than 15,000 pairs of twins have been enrolled in TEDS and the participating families are representative of the UK. The measures at 2, 3 and 4 years are administered by parents. At 7 years, children are assessed for language and cognitive development using telephone testing, parents and children are interviewed about behavior problems, and teachers also assess behavior problems as well as academic achievement. One set of findings is that the same genes largely contribute to both language and cognitive problems and the same genes affect normal and abnormal development, a result that suggests that general impairment may be a better target for genetic research than specific language impairment independent of nonverbal cognitive problems. DNA has been obtained so far for more than 4000 pairs and is being used initially in molecular genetic studies of language problems and hyperactivity.

T he Twins Early Development Study (TEDS) focuses on the early development of the three most common psychological problems in childhood: communication disorders, mild mental impairment and behavior problems. The TEDS twins were assessed longitudinally at 2, 3, 4 and 7 years of age in order to investigate genetic and environmental contributions to change and continuity in language and cognitive development; it is multivariate in order to examine the origins of comorbidity; and it uses a large sample in order to study abnormal development in the context of normal development. The twins were identified from birth records of twins born in the UK in 1994-96. More than 15,000 pairs of twins have been enrolled in TEDS and the participating families are representative of the UK. The measures at 2, 3 and 4 years are administered by parents. At 7 years, children are assessed for language and cognitive development using telephone testing, parents and children are interviewed about behavior problems, and teachers also assess behavior problems as well as academic achievement. One set of findings is that the same genes largely contribute to both language and cognitive problems and the same genes affect normal and abnormal development, a result that suggests that general impairment may be a better target for genetic research than specific language impairment independent of nonverbal cognitive problems. DNA has been obtained so far for more than 4000 pairs and is being used initially in molecular genetic studies of language problems and hyperactivity.The Twins Early Development Study (TEDS) is the first large-scale population-based twin study in the UK, and the largest study by far ever conducted on language and cognitive development. One reason for its size is to enable TEDS to investigate the genetic and environmental etiology of abnormal development in the context of normal development. A related goal is to study developmental problems in a representative community sample rather than studying children who were identified clinically because the latter are unlikely to be representative of children with such problems. Another reason why a large sample size is needed is that TEDS was also designed to foster collaborative research in a new interdisciplinary research centre called the Social, Genetic and Developmental Psychiatry (SGDP) Research Centre whose goal is to bring together genetic and environmental influences in the study of behavioral problems of development. Major Research FocusAlthough communication disorders, mild mental impairment, and behavior problems represent the most common behavioral disorders of childhood, little is known about their genetic and environmental origins . These disorders are frequently comorbid but nothing is known about the genetic and environmental links between them as they emerge in infancy and early childhood. Because these problems are often undetected until the school years, it is necessary to investigate them in a community sample in early childhood. These considerations provide the prim...