Up to 30% of children of parents with dyslexia develop this learning disorder, compared to only 3 percent of children with parents possessing normal to good reading skills. This is one of the results of the Dutch Dyslexia Programme (DDP, 1997-2012), a study conducted by researchers at the University of Amsterdam, Radboud University Nijmegen and the University of Groningen. The results of the study were published in The Journal of Child Psychology and Psychiatry.
During the study, more than 200 children with and without familial risk for dyslexia were monitored from the age of 2 months to 9 years old. It appears that the group of children at risk who became dyslexic read as much as three to four times more slowly compared to the control group of children. They also make twice as many errors in reading and spelling.
What is striking is that the children with familial risk who ultimately do not become dyslexic are weaker in reading and spelling. This shows that the risk of dyslexia can have a gradual progression and is not an "all or nothing" proposition. It seems that children at risk without dyslexia still inherit some of the many genes involved in dyslexia.
Dutch Dyslexia Programme (DDP)
Under the DDP, researchers from various disciplines, including neurology, psychiatry, psychology, pedagogy, genetics and linguistics. The programme consists of three components: long-term research, intervention research and genetic research. The above results come from the long-running investigation.
As part of the intervention research, the effectiveness of different therapies is being evaluated and researchers are attempting to identify the genetic factors involved in dyslexia within the genetic research component.
The DDP was funded by the Netherlands Organisation for Scientific Research (NWO).