Some children struggle to read or spell because of a condition called dyslexia that is known to run in families.
Now, researchers report they have pinpointed a large number of genes responsible for the disorder.
"Our findings show that common genetic differences have very similar effects in boys and girls, and that there is a genetic link between dyslexia and ambidexterity," said lead researcher Michelle Luciano, of the University of Edinburgh's School of Philosophy, Psychology and Language Sciences, in Scotland.
"Our results also suggest that dyslexia is very closely genetically related to performance on reading and spelling tests, reinforcing the importance of standardized testing in identifying dyslexia," Luciano said in a university news release.
To come to those conclusions, the researchers tested the association between millions of genetic variants and dyslexia status, finding 42 significant variants in the study, which included 50,000 adults diagnosed with dyslexia and 1 million adults without the diagnosis.
About one-third of the genetic variants identified had been previously linked to general cognitive ability and educational attainment. Some of the genes were associated with other neurodevelopment conditions, such as language delay, and with thinking skills and academic achievement. Many were novel and they could represent genes that more specifically associate with processes essential for learning to read, the study found.
Many of the genes linked to dyslexia are also associated with attention deficit hyperactivity disorder (ADHD), the study noted.
The study was the largest genetic study of dyslexia to date.
Researchers also found that several of the associated genetic variants were significant in a sample of Chinese-speaking participants in the study. This suggests that general thinking processes in learning to read are not dependent on a particular language.
Using genetic information from the study, the researchers were able to predict how well children and adults from four other studies could read.
The findings were published Oct. 20 in the journal Nature Genetics.
Other key researchers were from the Max Planck Institute for Psycholinguistics in the Netherlands, QIMR Berghofer Medical Research Institute in Australia and the U.S. company 23andMe Inc.
The U.S. National Institute of Neurological Disorders and Stroke has more on dyslexia.
SOURCE: University of Edinburgh, news release, Oct. 20, 2022