No evidence for association and linkage disequilibrium between dyslexia and markers of four dopamine-related genes.

Dopamine genes are candidate genes for dyslexia in the light of the well-known comorbidity between dyslexia and ADHD. Within-family association and linkage disequilibrium were tested between four genetic markers at DRD4, DRD3, DRD2, and DAT loci, and dyslexia, in a sample of 130 Italian dyslexic children, 16.9% of whom had comorbid ADHD. No evidence of either association or linkage disequilibrium was found, neither in the total sample nor in the comorbid subgroup. Negative results do not support a common genetic basis between these two disorders for these markers.