Genetic Influences on Learning Disabilities: An Update

The present selective review examines genetic influences on learning disabilities (LDs). We discuss recent advances in molecular genetics that have made linkage analysis a more powerful tool for studying the genetics of behavioral phenotypes. We also examine what is known about genetic influences in two familial disorders, developmental dyslexia and Tourette syndrome (TS). Although TS is not a LD, there are claims that it is associated with LDs as well as with other related behavioral phenotypes. We briefly consider an opposite strategy for examining genetic influences on LDs, that is, by beginning with a known genetic alteration and examining whether it leads to a specific LD phenotype. We also discuss criteria that must be satisfied before we can conclude either that a phenotype is genetically influenced or that a known genetic alteration leads to a specific and consistent cognitive phenotype. When these criteria are met, the study of genetic influences on LDs can be a powerful method for informing us about the neurobiology of cognitive development.