The genetic predisposition for ADHD overlaps with the genetic predisposition for dyslexia and dyscalculia. This shared genetic risk explains why pupils with ADHD are more likely to experience difficulties with reading, spelling, and math. This study, conducted on 20,000 Dutch children, was led by biological psychologists from VU Amsterdam and UvA.
Dyslexia and Dyscalculia
The study, published in Psychological Science, found that 37% of children with ADHD also have dyslexia or dyscalculia. Learning problems do not arise because of ADHD itself, but rather because the genetic predisposition for ADHD also increases the risk of severe difficulties with reading, spelling, and math. Children with ADHD often struggle to concentrate and may be hyperactive and impulsive. Children with dyslexia have difficulty with spelling and fluent reading, while children with dyscalculia struggle with arithmetic and maths.
Heritability
This research demonstrates that the overlap between these conditions is not due to one condition causing the other, but rather due to shared genetic risk factors. “Education is crucial for learning to read, spell, and do maths. Despite good education, children differ in how easily they acquire these skills. Those individual differences are 75% due to genetic predisposition,” says lead scientist Elsje van Bergen from the Vrije Universiteit Amsterdam. “It is especially important to provide high-quality education to children predisposed to conditions like dyslexia.”
Remedy
These findings have significant implications for education and clinical practice. Treating ADHD alone is unlikely to improve academic skills, and conversely, treating a learning disorder like dyslexia will not necessarily reduce ADHD symptoms. “So, a remedy for one is not a remedy for the other,” says co-researcher Kees-Jan Kan from the University of Amsterdam.
Twins
The study was conducted among participants from the Netherlands Twin Register. The sample included twin children between the ages of 7 and 10, as well as their siblings, parents, and teachers. Identical twins resemble their twin more closely than fraternal twins, not only in appearance but also in ADHD behaviours and academic skills. Identical twins share the same DNA, while fraternal twins share, on average, 50% of their DNA, as do regular siblings. The psychological scientists used this information in their calculations.