Dyslexia is partly inherited, as the tendency to develop dyslexia runs in families. By studying genetic markers in families in which there is a high incidence of dyslexia, scientists have now identified genes on at least eight different chromosomes as having some role or connection with dyslexia. No single gene is involved in all cases of dyslexia. It is probable that dyslexia is influenced by a combination of genes; these genes may also influence different aspects of physical or intellectual development.

However, because your child's brain continues to grow and develop from birth through adulthood, dyslexia is also influenced by your child's learning experiences and environmental factors. This may explain why the specific symptoms of dyslexia can be so variable, and why some children have much more serious reading problems than others.

Studies of identical twins have shown that where one twin is dyslexic, the other will have dyslexia about 55 to 70 percent of the time, depending on the type of dyslexia. This research shows that there is a strong genetic influence, but that environmental factors also play a part.