For the first time, scientists have identified a large number of genes that are consistently linked to dyslexia. A third of the 42 identified genetic variants have previously been linked to general cognitive ability and educational attainment.
The findings, which were published in the journal Nature Genetics, are said to help us understand the biology behind why some children struggle to read or spell. Dyslexia is known to run in families, thanks in part to genetic factors, but until now, little was known about the specific genes associated with the risk of developing it.
The University of Edinburgh is leading the largest genetic study of dyslexia to date. Previous studies linking dyslexia to specific genes were conducted on a small number of families, and the evidence was unclear, according to the research team.
This most recent study included over 50,000 adults who had been diagnosed with dyslexia and over one million adults who had not. Researchers examined the relationship between millions of genetic variants and dyslexia status and discovered 42 significant variants.
Our findings show that common genetic differences have very similar effects in boys and girls, and that dyslexia and ambidexterity have a genetic link. Our findings also suggest that dyslexia is strongly linked to performance on reading and spelling tests, emphasizing the importance of standardised testing in identifying dyslexia.
Dr. Luciano
Some of these are associated with other neurodevelopment conditions, such as language delay, and with thinking skills and academic achievement. Many, however, are novel and could represent genes that more specifically associate with processes essential for learning to read.
Many of the genes associated with dyslexia are also associated with attention deficit hyperactivity disorder. A much smaller overlap of the genes associated with dyslexia was found for psychiatric, lifestyle, and health conditions.
Several of the associated genetic variants were also significant in a Chinese speaking sample suggesting that there are general cognitive processes in learning to read that are not dependent on the type of language.
Using the genetic information from the study, researchers claim they were able to predict how well children and adults from four other research studies could read and spell, but not with the accuracy required for diagnostic use.
Other key researchers in the study came from the Netherlands’ Max Planck Institute for Psycholinguistics, Australia’s QIMR Berghofer Medical Research Institute, and the US company 23andMe, Inc.
Lead researcher Michelle Luciano, of the University of Edinburgh’s School of Philosophy, Psychology and Language Sciences, says the study sheds light on many unanswered questions around dyslexia.
“Our findings show that common genetic differences have very similar effects in boys and girls, and that dyslexia and ambidexterity have a genetic link,” says Dr. Luciano. “Previous research suggested that some brain structures may be altered in people with dyslexia, but we found no evidence that genes are to blame. Our findings also suggest that dyslexia is strongly linked to performance on reading and spelling tests, emphasizing the importance of standardised testing in identifying dyslexia.”
