Genetic associations between ADHD symptoms and cognitive measures.

Introduction: ADHD is a highly heritable disorder but gene finding studies have been unsuccessful so far. Cognitive traits like executive functions, IQ and academic achievement measures have been associated to ADHD. These associations may direct to biological mechanisms, and related genes, that are involved in ADHD. Methods: The current study investigated the etiology of the relation between ADHD related symptoms and educational achievement. Subjects were 568 Dutch twin pairs. Maternal ratings on ADHD symptoms were assessed at age 5 and at age 7. Academic achievement was measured with standardized tests on mathematics, comprehension, reading and spelling in grade 2, 4 and 6. Results: Results show that ADHD related symptoms correlated around -0.20 with comprehension and mathematics, and around -0.12 with reading and spelling on a phenotypic level. Phenotypic correlations were predominantly determined by genetic factors; environmental factors did not contribute to the association. Discussion and conclusion: Previous studies reported genetic associations between IQ and ADHD related symptoms. The genetic overlap in ADHD and cognitive measures shows that cognitive abilities should be taken into account regarding etiological factors of the disorder. [ABSTRACT FROM AUTHOR]