Inzichten uit onderzoek naar kinderen met een familiair risico op dyslexie

It has been known for some time that dyslexia runs in families. Children with a parent with dyslexia have an elevated risk of developing reading and spelling problems. In several familiar risk (FR) studies on dyslexia, children with a familiar risk for dyslexia were followed for several years, often even from birth. Such FR-studies provide interesting insights about the etiology and development of dyslexia. In the Netherlands a large-scale study, the Dutch Dyslexia Program, has been conducted. In this paper we provide an overview of the results of this study with respect to two questions. The first question concerns the differences between FR-children with and without dyslexia, and control children without a familiar risk. As expected, the FR-children with dyslexia lagged behind on a range of cognitive reading-related factors. Interestingly, these children also had a somewhat higher familiar risk for dyslexia than the FR-children without dyslexia. The parents of the FR-children with dyslexia read more poorly than the parents of the FR-children who did not develop dyslexia. The FR-children without dyslexia had, as compared to the control group, mild problems in reading and spelling as well as a small lag on the precursors of reading. The second question was about the effect of FR on the pathways into literacy, word reading and reading comprehension. Children were followed during the period from 4 to 12 years of age, i.e. halfway Grade 6. Family risk for dyslexia had a negative impact on the development of both word reading and reading comprehension. The influence of FR on word reading was partly mediated by the precursors of reading, but FR also had a direct effect. Unexpectedly, FR appeared to have an independent effect on reading comprehension in sixth grade. Familiar risk did not have an effect on the development of vocabulary, often considered, besides word reading, as a major factor fueling the development of reading comprehension. The theoretical and practical implications of these findings are discussed.