New research finds ADHD ‘is a genetic disorder’

30^th September 2010 - Scientists say they have found the first direct evidence that Attention Deficit Hyperactivity Disorder (ADHD) is a genetic condition. They say their findings provide proof that ADHD cannot be blamed on bad parenting or poor diet and hope that the research removes the stigma associated with the condition.

ADHD affects around one in 50 children and makes them restless, impulsive and easy to distract. Children with ADHD develop problems at home and at school. There is no cure for the condition, but symptoms can be treated with medications and behavioural techniques.

Scientists at the MRC Centre in Neuropsychiatric Genetics and Genomics and Department of Psychological Medicine and Neurology, Cardiff University, and colleagues, set out to confirm previous studies that suggested genetics lay behind the development of ADHD.

ADHD in the family

“We’ve known for many years that ADHD may well be genetic because it tends to run in families,” lead investigator, Professor Anita Thapar, told a news conference at The Science Media Centre in London. “What’s really exciting now is we’ve found the first direct genetic link to ADHD.”

The team analysed the DNA of 366 children with ADHD and 1,047 without the condition. They found that children with ADHD were more likely to have chunks of DNA segments which are either duplicated or missing than participants who did not have the condition. They say this type of genetic variation is found to be more common in brain disorders, therefore providing the first direct evidence that ADHD is a neurodevelopmental disorder.

Overcoming the stigma

"We hope that these findings will help overcome the stigma associated with ADHD," says Thapar. "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."

The findings came as no surprise to Jacqui Vango, Secretary of the ADHD charity Misunderstood . She tells us that any research which debunks the myth that ADHD is down to bad parenting is to be welcomed. Vango, who has two grandchildren diagnosed with the condition, says: “Kids with ADHD have a hard time. If they get to a school that knows about it, and see the kids with ADHD as a challenge, then those children can achieve great things.

“We get calls from all over the country and all we get is: ‘it's difficult to get our child diagnosed and if they are diagnosed they just get chucked in the corner because they’re naughty’.”

ADHD and other brain disorders

At the press conference to launch the latest research, Thapar said that they had also come to another “exciting” conclusion: that the genetic irregularities in children with ADHD overlapped with chromosomal regions that have previously been implicated in two brain disorders - autism and schizophrenia. The authors say that, whilst these conditions are currently thought to be entirely separate, autism and ADHD have similar symptoms and both give rise to learning difficulties. The team say their research suggests there may be a shared biological basis to these two conditions. 

"Children with ADHD have a significantly higher rate of missing or duplicated DNA segments compared to other children and we have seen a clear genetic link between these segments and other brain disorders," says one of the authors, Dr Nigel Williams, in a statement. "These findings give us tantalising clues to the changes that can lead to ADHD."

The study is published in The Lancet Online First.