30 Sep 2010

ADHD linked to faulty genetics

Attention Deficit Hyperactivity Disorder is a genetic condition rather than a bad diet or poor parenting skills, new research suggests. Kylie Morris looks into the data.

Scientists at Cardiff University say a new study has uncovered a genetic link between children diagnosed with ADHD, which they hope will reduce the stigma associated with the disorder.

Researchers found that rare copy number variants – where small segments of DNA are duplicated or missing – were twice as common in children with ADHD than those without the condition.

The research, published in The Lancet, found there was an overlap between the affected parts of the DNA and those associated with autism and schizophrenia.

The most significant overlap was found at a particular region on chromosome 16, which has previously been implicated in schizophrenia and other psychiatric disorders and spans a number of genes including one known to play a role in the development of the brain.

Around one in 50 UK children are affected by ADHD, making them restless, impulsive and easily distracted, often causing them problems at school and home. Medical and behavioural therapy can help reduce symptoms but there is no cure for the disorder.

Scientists said they hoped the findings would improve understanding of the disorder which has provoked controversy in the past. Although children with ADHD are statistically more likely to have a parent with the condition, there has been no direct scientific link to show it was genetic.

“We hope that these findings will help overcome the stigma associated with ADHD,” said Professor Anita Thapar, from the Department of Psychological Medicine and Neurology.

“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.”

Uncovering clues
The researchers analysed the genomes of 366 children diagnosed with ADHD against more than 1,000 control samples to search for variations in their genetic make-up.

They found 57 large, rare copy number variants in the ADHD sufferers compared with 78 among the 1,047 controls.

Nigel Williams, also from the Department of Psychological Medicine and Neurology, said: “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.

“These findings give us tantalising clues to the changes that can lead to ADHD.”