Over range of ADHD behavior, genes major force on reading achievement, environment on math

April 22, 2011

Humans are not born as blank slates for nature to write on. Neither are they behaving on genes alone.

Research by Lee A. Thompson, chair of Case Western Reserve University's Psychological Sciences Department, and colleagues found that the link between Attention-Deficit/Hyperactivity Disorder (ADHD) and academic performance involves a complex interaction of genes and environment.

Genetic influence was found to be greater on reading than for math, while shared environment (e.g., the home and/or school environment the twins shared) influenced math more so than reading. The researchers don't know why.

Their study of twins, published in Psychological Science, Vol. 21, was the first to look simultaneously at the genetic and environmental influences on reading ability, mathematics ability, and the continuum of ADHD behavior.

"The majority of the twins used in the study don't have ADHD," Thompson said. "We are looking at the continuum of the behavioral symptoms of ADHD - looking at individual differences - not a disorder with an arbitrary cutoff."

This type of continuum is a normal distribution or bell curve, with scores symmetrically distributed about the average and getting much less frequent the farther away a score is from the average. Disability is usually classified as the lower extreme on the normal distribution.

The symptoms of ADHD, according to Thompson, can be described with such a continuum, as can reading and mathematics ability. Only a small percent of individuals fall below the common medical cutoff between ability and disability.

For what we refer to as gifted or disabled, Thompson points out, "There is no difference in cause, just different expression of achievement."

Thompson collaborated with Sara Hart, a graduate student at the Florida Center for Reading Research, and Stephen Petrill, a professor at the Ohio State University, in analyzing 271 pairs of ten-year-old identical and fraternal twins.

The twins were selected from the Western Reserve Reading and Mathematics Project, a study that began in 2002 with kindergarten and first grade-age twins and has collected data yearly about their math and reading ability.

The study focused on two ADHD symptoms: inattention and hyperactivity, which are viewed as extremes of their respective attention and activity continuums.

As part of the study, the mother of the twins rated each child on 18 items such as the child's ability to listen when spoken to, play quietly, and sit still, to assess attention and activity levels. A researcher testing each twins' mathematics and reading ability also rated the twins each year on their attention to tasks and level of hyperactivity.

The researchers assessed reading ability by evaluating the twins' recognition and pronunciation of words and passage comprehension.

They measured the twins' capacity for mathematics by focusing on the twin's ability to solve problems, understanding of concepts, computational skills, and the number of computations completed in 3 minutes.

Researchers analyzed the data from three perspectives: one looked at the overall ADHD behavior, one at the level of attention, and at the activity level.

They then determined the similarities in genetic and environmental influence between ADHD symptoms and reading and between the symptoms and mathematics.

To do so, researchers looked at the variance and covariance of ADHD symptoms and academic ability. Variance measures the individual differences on a given trait within a population and covariance is a measure of how much two traits are related.These measures were broken down into identified components: additive genetic effects, shared environment and non-shared environment.

Using quantitative analysis of the components, the researchers found that there are some general genes that influence the symptoms of ADHD simultaneously with reading and mathematics ability and some genes that influence each specifically.

This study also found that both inattention and hyperactivity were related to academics.

"If we have this much overlap between genes that affect behaviors of ADHD and academic achievement," Thompson said, "it gives validity to the relation of ADHD behaviors and poor academics."

But genes are not everything, Thompson adds.

There are different approaches for interventions that can be taken based on the extent of environmental influence on ADHD behavior, reading ability, and mathematics ability across the entire continuum of expression.

Future research, the study notes, should focus on the underlying connection between ADHD symptoms and poor academic achievement in order to identify the influences that may alter these often co-occurring outcomes.
-end-
Additional authors include Erik Willcutt from the University of Colorado, Boulder; Christopher Schatschneider from Florida Center for Reading Research, Florida State University; Kirby Deater-Deckard from Virginia Polytechnic Institute and State University; and Laurie E. Cutting from Vanderbilt University.

Funding for the study was provided by the National Institute of Child Health and Human Development and by the Department of Education. Sara Hart was additionally supported by the Lucile and Roland Kennedy Scholarship Fund in Human Ecology from the Ohio State University and the P.E.O. Scholar Award.

Reference: S Hart et al. Exploring How Symptoms of Attention-Deficit/Hyperactivity Disorder Are Related to Reading and Mathematics Performance: General Genes, General Environments. Psychological Science. DIO:10.1177/0956797610386617 (2010).

Contact: Lee A. Thompson, Case Western Reserve University, lat@case.edu

Release prepared by Sarah Gavac, Case Western Reserve University

Case Western Reserve University

Related ADHD Articles from Brightsurf:

Autism and ADHD share genes
Researchers from the national psychiatric project iPSYCH have found that autism and ADHD share changes in the same genes.

ADHD across racial/ethnic groups
This study of patients from diverse racial/ethnic backgrounds who received care at the Kaiser Permanente Northern California health system looked at how common attention-deficit/hyperactivity disorder (ADHD) diagnoses were over a 10-year period across seven racial/ethnic groups.

Cycles of reward: New insight into ADHD treatment
Researchers at the Okinawa Institute of Science and Technology Graduate University (OIST) in collaboration with scientists at the University of Otago and the University of Auckland in New Zealand, investigated the actions of the drug in rats.

Young mums more likely to have kids with ADHD
Young mothers have a greater chance of having a child with attention deficit hyperactivity disorder (ADHD) according to new research from the University of South Australia.

ADHD medication: How much is too much for a hyperactive child?
When children with ADHD don't respond well to Methylphenidate (MPH, also known as Ritalin) doctors often increase the dose.

Antipsychotic use in youths with ADHD is low, but still cause for concern
A new study eased fears about the proportion of youths with ADHD taking antipsychotic drugs, but still found that many prescriptions may be inappropriate.

How stimulant treatment prevents serious outcomes of ADHD
Analysis quantifies the extent which stimulant treatment reduces serious outcomes in children and young adults with ADHD.

Did Leonardo da Vinci have ADHD?
Leonardo da Vinci produced some of the world's most iconic art, but historical accounts show that he struggled to complete his works.

More sleep may help teens with ADHD focus and organize
Teenagers with attention deficit hyperactivity disorder (ADHD) may benefit from more sleep to help them focus, plan and control their emotions.

Researchers have found the first risk genes for ADHD
A major international collaboration headed by researchers from the Danish iPSYCH project, the Broad Institute of Harvard and MIT, Massachusetts General Hospital, SUNY Upstate Medical University, and the Psychiatric Genomics Consortium has for the first time identified genetic variants which increase the risk of ADHD.

Read More: ADHD News and ADHD Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.