ADHD and reading disability have common genetic influences

Washington, Dec 9 : A new study has revealed how Attention Deficit Hyperactivity Disorder (ADHD) and developmental reading disability (RD) in children frequently occur together.

If a child is experiencing trouble with reading, symptoms of ADHD are often also present. However, the reason for this correlation remains unknown.

The new study has suggested that the childhood disorders have common genetic influences, which may also lead to slow processing speed - the brain taking longer to make sense of the information it receives.

The researchers looked at 457 pairs of twins from the Colorado Learning Disabilities Research Center (CLDRC) twin study - an ongoing study of the causes of reading disabilities, ADHD, and related disorders.

Erik Willcutt and colleagues compared groups of participants with and without RD and ADHD, using a variety of tests to measure general cognitive ability, processing speed, reading and language skills, and then analysed results from pairs of twins within those groups to determine the genetic causes of any correlations.

The findings showed that both RD and ADHD are complex disorders, influenced by many factors; ADHD on its own was associated with a reduced ability to inhibit responses to stimuli, while reading disabilities were associated with various weaknesses in language and memory.

However, both disorders were associated with a slow processing speed and the twin-analyses further revealed a significant genetic correlation between RD and ADHD, i.e., a participant with one of the disorders was more likely to show symptoms of the other.

The finding has been reported in the latest special issue of Cortex.

--ANI

View the original article here

Twin study helps scientists link relationship among ADHD, reading, math

ScienceDaily (Dec. 10, 2010) ? Children with ADHD can sometimes have more difficulties on math and reading tests compared to their peers. A new study published in Psychological Science, a journal of the Association for Psychological Science, used identical and fraternal twins to look at the genetic and environmental influences underlying ADHD behaviors, reading, and math skills in children in an attempt to better understand the relationship among them.

Sara Hart, of the Florida State University, and her colleagues used twins enrolled in a long-term study of reading and math. Hart says by focusing on twins specifically, psychological scientists are able to tease out the difference between nature and nurture.

To do this, scientists compare identical twins, who have nearly the same DNA, with fraternal twins, who generally only share about half of their DNA. If identical twins are generally more alike on a trait -- say, their eye color or reading ability -- and fraternal twins are much less alike on the same trait, you can presume the trait is inherited. On the other hand, if pairs of identical twins are alike on a trait to the same extent that pairs of fraternal twins are alike on that trait -- like how outgoing they are -- you know the trait is probably influenced by their environment. Most traits fall somewhere in between, and twin studies can show that, too.

In this case, Hart and her colleagues were interested in how twins matched up on symptoms of ADHD, reading achievement, and math achievement. At about age 10, every pair of twins was tested on their reading and math ability. Their mothers also filled out surveys on any problems the children have with attention or hyperactivity.

The researchers found that ADHD behaviors, reading achievement, and math achievement were all influenced by the same genetic influences; this doesn't prove anything about what causes what, but some psychological scientists think that all three might be linked through the working memory system.

Although common genetic influences is a typical result from twin studies, the exciting aspect of this work was that that ADHD behaviors, reading achievement, and math achievement are also associated by common environmental influences.

Although it is not known what the actual environmental influences are, Hart and her colleagues suggest that it could be related to aspects of the classroom and homework environment. If researchers can figure out what these environmental influences really are, they may be able to help children with ADHD do better in school.

Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Association for Psychological Science.

Journal Reference:

Sara Hart et al. Exploring How Symptoms of Attention-Deficit/Hyperactivity Disorder Are Related to Reading and Mathematics Performance: General Genes, General Environments. Psychological Science, (in press)

Note: If no author is given, the source is cited instead.

View the original article here