Why children with ADHD are more likely to have a parent with ADHD

Researchers report the first genetic link to ADHD.
Written by Boonsri Dickinson, Contributing Editor

People have blamed anything from poor parenting to candy filled diets for causing attention-deficit/hyperactivity disorder (ADHD), but now there's evidence that the disorder is genetic.

In fact, researchers are finding evidence that the brains of children with ADHD develop differently.

Children with ADHD are often troublesome in the classroom because they have a hard time concentrating. They fidget, squirm, daydream, can't sit still, blab a lot, interrupt others, don't like to listen, and are impulsive.

Since 2006, 4.5 million children from 5 to 17 years old have been diagnosed with the disorder, according to the Centers for Disease Control and Prevention —millions are medicated with drugs like Ritalin and Adderal. Last year, the ADHD drugs sold for $4 billion.

Cardiff University researchers found the first direct evidence that children with ADHD have genetic variants that cause this developmental disorder. By looking at the copy number variants (CNVs), the scientists found that regions of the DNA had been duplicated or were just flat out missing.

CNVs are seen in other types of brain disorders such as autism and schizophrenia.

The study was published in the Lancet. In it, the researchers compared 366 children with ADHD and 1047 children without it.

"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," Dr Nigel Williams, School of Medicine said in a statement. "These findings give us tantalizing clues to the changes that can lead to ADHD."

The researchers found direct genetic difference in patients with ADHD. The children with ADHD had a marked two fold increase of rare CNVs than the control group.

Knowing more about the biology might lead to better treatments. But don't expect a simple diagnostic test to roll out — the genetic variations aren't that simple and there are a host of environmental factors to account for.

Indeed, the evidence is growing that ADHD is an early onset brain disorder. The researchers hope this study lessens the stigma that often goes with an ADHD diagnosis.

But the jury is still out about the biological underpinnings of ADHD. Fergus Walsh wrote in a BBC blog post:

There is a danger of reading too much into new research in the Lancet... Like many disorders, there is no simple cause behind ADHD. Simply blaming poor parenting is surely as bad as saying it's all down to our genes. Parents of children with ADHD would prefer help rather than labels.

Photo: CDC

This post was originally published on Smartplanet.com

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