The latest study shows evidence of a genetic link to attention-deficit hyperactivity disorder or ADHD. The researchers from Cardiff University, Wales said the disorder was a brain problem like autism and not due to bad parenting. The paper appeared in the acclaimed journal Lancet.
ADHD typically presents with restlessness, impulsive and often aggressive nature along with destructive tendencies and inattention. School performance and family life suffers terribly.
For the study the team analyzed stretches of DNA from 366 children who had been diagnosed with the disorder. They compared the DNA with that of 1,047 people without the condition. They found that 15% of the ADHD group had large and rare variations in their DNA - compared with 7% in the control group.
According to researcher Professor Anita Thapar of Cardiff University in Wales, “We found that, compared with the control group, the children with ADHD have a much higher rate of chunks of DNA that are either duplicated or missing…This is really exciting - because it gives us the first direct genetic link to ADHD…We have looked at lots of potential risk factors in the environment - such as parenting or what happens before birth - but there isn't the evidence to say they're linked to ADHD…There's a lot of public misunderstanding about ADHD. Some people say it's not a real disorder, or that it's the result of bad parenting…Finding this direct link should address the issue of stigma.”
However the authors of the study agree that there is no single gene behind ADHD, and the work is at too early a stage to lead to any test for the disorder. But there is hope for uncovering biological basis of ADHD and also new therapies.
In an editorial accompanying the paper in the same issue, J. Peter Burbach, of University Medical Center Utrecht in the Netherlands, said the findings are exciting, but noted that they had unclear clinical significance. “The first gains beyond today's study might be initial insights into the pathogenesis and neurobiology of brain development as influenced by these genetic variants,” he wrote. “This knowledge will eventually enter the clinic and might affect the way people think about and treat neurodevelopmental disorders by accounting for the biological consequence of the specific patient's genotype,” Burbach added.
The study faced criticism from clinical child psychologist and broadcaster, Oliver James. He pointed out that there were other studies which looked at the effect of anxiety among pregnant women, and disturbed early relations between mothers and their babies. He said, “Only 57 out of the 366 children with ADHD had the genetic variant supposed to be a cause of the illness…That would suggest that other factors are the main cause in the vast majority of cases…Genes hardly explain at all why some kids have ADHD and not others.”
Philip Asherson, a professor of molecular psychiatry at the Institute of Psychiatry at King's College London agreed saying, “Environmental factors such as severe social deprivation at an early age should still be considered a cause of the disorder…The study doesn't tell us a lot about what's going on in the brains of people with ADHD…If we can find out more about these genes and how they affect brain development, that may give us inroads, but it's hard to say when that will be.”
The study was funded by Action Research, Baily Thomas Charitable Trust, the Wellcome Trust, Britain's Medical Research Council and the European Union.
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