Origins of learning difficulties and behaviour problems: from behavioural genetics to behavioural genomics

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Learning difficulties and their associated behaviour problems incur major social cost because they affect so many children and their families, they often persist into adolescence and adulthood, and their effects spill into many areas of children?s lives. Understanding the genetic and environmental origins of these problems is critical to predicting and preventing them. Since 1995, MRC programme grant G500079 has provided continuous support for the UK Twins Early Development Study (TEDS) on the genetics of learning difficulties and associated behaviour problems in childhood, the world?s largest study of twins assessed from infancy to adolescence. TEDS findings have led to new ways of thinking about the genetic and environmental origins of learning difficulties and behaviour problems in childhood, most notably a ?generalist genes? theory of learning difficulties. These findings have charted the course for molecular genetic research that has begun to identify genes responsible for the substantial genetic influence on these disorders. During 2010-15, we will capitalise on this 15-year programme of research by assessing 5000 pairs of at age 16, a crucial developmental turning point socially and biologically coming as it does at the end of compulsory education and near the end of puberty. Using Web-based tests that have been developed as part of TEDS, we will test the twins for aspects of learning that have proven most important and interesting in our research: reading, language and speech, mathematics, science, and general cognitive ability. We will also assess school performance (GCSE), behaviour problems, and home and school environments. This research is not merely about the nature-nurture issue of how much genetics affects learning difficulties and their associated problems. The classic twin design comparing identical and non-identical twins allows us to ask key questions about development (e.g., do genetic effects change from age to age?), about links between disorders (e.g., do different genes affect different disorders such as reading and mathematics?), and about the interplay between genes and environment (e.g., do genes affect our experiences?). Great value has been added to TEDS by obtaining two million DNA markers on 4000 of the TEDS children, which will make it possible for the first time to conduct systematic searches across the genome for genes responsible for these genetic effects. Finding these genes will make it possible to identify children at risk long before they fail in school and to foster environmental interventions that prevent the onset of these disorders.