British Researchers Find First Evidence Of Genetic Link To ADHD

Often ADHD is ignored as an explanation for bad behavior.: image via healthyfellow.comIn the 1980's when attention-deficit/hyperactivity disorder (ADHD) was first bandied about as a developmental disability, many college and university administrators and teachers thought it was just an excuse for poor grades and low test scores. Slowly though, it has become recognized in the educational community as an actual disorder and new educational methods, as well has drugs, have been developed to help treat it.  Now, scientists have found that there is a genetic link to ADHD.

Scientists at the University of Cardiff in the UK analysed the genomes of 366 children clinically identified as ADHD, comparing them to the genomes of 1,000 children who did not have ADHD.  The researchers found a significant difference in copy number variants (CNVs) between the two groups, as well as genetic variants of the ADHD children, primarily affecting chromosome 16, seen as well in autistic and schizophrenic identified disorders.

Though the condition is highly inheritable, until now there has been little evidence of genetic involvement.  ADHD has been attributed to anything from poor parenting to poor diet. This research offers the first proof that ADHD is a neurodevelopmental disorder.

"We hope that these findings will help overcome the stigma associated with ADHD," said Professor Anita Thapar, one of the researchers on the Cardiff team. "Too often, people dismiss ADHD as being down to bad parenting or poor diet. As a clinician, it was clear to me that this was unlikely to be the case. Now we can say with confidence that ADHD is a genetic disease and that the brains of children with this condition develop differently to those of other children."

Dr John Williams, Head of Neuroscience and Mental Health at the Wellcome Trust, one of the sponsors of the ADHD research, which has supported Professor Thapar's work for ten years, said: "These findings are testament to the perseverance of Professor Thapar and colleagues to prove the often unfashionable theory that ADHD is a brain disorder with genetic links. Using leading-edge technology, they have begun to shed light on the causes of what is a complex and often distressing disorder for both the children and their families." The research is published in today's edition of the journal Lancet.

Children with ADHD typically show symptoms of the disorder, like inability to concentrate, forgetfulness, talking incessantly, interruptive behavior, and general hyperactivity, between the ages of 2 and 4 years of age.  These symptoms become more pronounced when they go to school, and later, in their teens, the disorder may lead to great frustration and even violent behaviors if not treated. 

State-based Prevalence Data of ADHD Diagnosis: image from U.S. Centers For Disease Control

The Centers for Disease Control data indicates that 4 percent of children ages 4 to 8 are reported with an ADHD diagnosis; among children 9 to 12 and 13 to 17, the incidence is 9.7 percent and roughly half of those professionally diagnosed are taking special medications for the condition. Of course, the incidence of  ADHD is under-reported because of the numbers of children not evaluated professionally or even by their parents, who may think their children are simply unruly.

ADHD is highest among white children with parents with minimum education, and it is higher in boys (9.5%) than girls (5.5%). Diagnosis is higher among health-insured children (which makes sense) and it varies by state (see above image.)

sources: Center for Disease Control, Science Daily, Reuters, via US News