Are Reading Disorders Hereditary?

by Dynaread

Research suggests that reading disorders or struggles are caused by the interaction between genetic and environmental factors which will produce a higher or lower risk of having dyslexia (Snowling, et al., 2003). Environmental factors have to do with how much the growing child has been exposed to language and print, for example, parents reading books aloud to their children or dinner table conversations. However, science agrees that reading disorders do run in families, so parents with reading disorders are likely to have children with reading disorders (Lagae, 2008).There is about 50% chance of a boy having dyslexia if his father has a reading disability and about 40% if his mother has a reading disorder; the chances are lower for girls (Snowling, 2004). It is clear then that a parent with dyslexia will not automatically have a child with dyslexia.

The genetics of reading disorders have been studied for the past 25 years and different studies have linked four genes to dyslexia. (Galaburdaet al., 2006, Harlaar, et al., 2007; Kovas et al., 2007; Snowling etal., 2003). In general, these genes are related to brain development; hence what is inherited is not the reading disability itself butthe manner in which the brain development differs from most, resulting in the difficulties with phonological processing that typically underlie dyslexia. It has been shown that identical twins have a higher probability of having dyslexia (58%) than non-identical twins (39%) (Lagae,2008).

Snowling and colleagues (2003) followed children from families with reading disorders during 5 years and found that around 60% of these high-risk children were identified as dyslexic. The remaining group did not fulfill the criteria for dyslexia but nevertheless showed mild weaknesses in reading-related skills (e.g., spelling, non-word reading, phonological awareness and reading comprehension), as compared to typically developing children. This finding matches other research concluding that family risk of dyslexia is continuous, meaning reading disorders are not an all-or-none condition and that children born in families with a history of reading disorders have an increased risk of struggling with reading at different levels (Pennington & Lefly, 2001). In those inheriting the brain development abnormalities, the seriousness of the problem will depend on how affected the component skills are (e.g., phonological processing, language skills) and the early compensation strategies adopted (Snowling et al., 2003).

Application

Since family background is a major factor in the early identification of children at risk of reading difficulties, it is highly recommended to screen these children by doing a dyslexia test at an early age (KG-Grade1) and —if indeed at risk — provide these children early on with appropriate reading instruction programs. In the future, genetics will probably help to select children at risk for reading disorders as well (Lagae, 2008; Snowling et al., 2003).

References

Galaburda,A. M., LoTurco, J., Ramus, F., Fitch, R. H., and Rosen, G. D. "From genes to behavior in developmental dyslexia" Nature Neuroscience. 9.10 (2006): 1213-1217. Print.

Harlaar, N., Dale, P.S., and Plomin, R. "From learning to read to reading to learn: Substantial and stable genetic influence" Child Devevelopment. 78.1 (2007): 116—131. Print.

Kovas, Y., Haworth, C. M. A., Harlaar N., Petrill, S. A., Dale, P. S., andPlomin, R. "Overlap and specificity of genetic and environmental influences on mathematics and reading disability in 10-year-old twins" Journal of Child Psychology and Psychiatry, 48.9 (2007): 914—922.Print.

Lagae, L. "Learning Disabilities: Definitions, Epidemiology, diagnosis, and intervention strategies" Pediatric Clinics of North America. 55. (2008): 1259—1268. Print.

Pennington, B., and Lefly, D. "Early reading development in children at family risk for dyslexia" Child Development.72.3 (2001): 816—833. Print.

Snowling, M. "The science of dyslexia: A review of contemporary approaches" The Study of Dyslexia . Ed. M. Turner and Ed. J. Rack.New York: Kluwer Academic Publishers, 2004. 77-90. Print.

Snowling, M.J., Gallagher, A., and Frith, U. "Family risk of dyslexia is continuous: Individual differences in the precursors of reading skill" Child Development, 74.2 (2003): 358—373.Print.