Gene Disorder Linked to ADHD09/30/10
WEDNESDAY, Sept. 29 (HealthDay News) -- Many who suffer from
attention-deficit hyperactivity disorder (ADHD) appear to have a
genetic abnormality that may predispose them to the condition,
British researchers report.
Their finding bolsters the belief that ADHD is not solely a
social problem but can have origins in an individual's biology.
ADHD affects 3 percent to 5 percent of children in the United
States, according to the U.S. National Institute of Mental
"ADHD is a complex disorder, and we have known for quite some time that it has a strong genetic composition," said lead researcher Nigel Williams, a senior lecturer in the department of psychological medicine and neurology at the Cardiff University School of Medicine in England.
"This is directly supported by our results, which provide direct evidence that ADHD is a neurodevelopmental disorder," he said.
The report is published online Sept. 30 in
For the study, Williams' team analyzed DNA from 366 children
with ADHD, comparing it with the DNA from 1,047 children without
Children with ADHD were more likely to have missing or
duplicated segments of DNA -- called copy number variations (CNVs)
-- than were children without ADHD, the researchers found. This
type of genetic variation is more common in those with brain
disorders, they noted.
In addition, they reported finding significant overlap between
these CNVs and CNVs associated with autism and schizophrenia.
Though they are separate conditions, there's some overlap between
ADHD and autism in terms of symptoms and learning problems, so the
two conditions might share a biological basis, the researchers
The most striking overlap, they said, was found on a region of
chromosome 16 that has been linked to schizophrenia and other major
psychiatric disorders and includes a gene that plays a role in the
development of the brain.
Children with ADHD tend to be restless, impulsive and easily
distracted, often leading to serious problems at home and at
school. Some have blamed the condition on such things as bad
parenting and high-sugar diets.
However, others have cited evidence that ADHD may be partly
genetic. Children of someone with ADHD have been shown to be more
likely to have the condition. Other research has reported that,
with identical twins, if one twin has ADHD, the other has a 75
percent chance of having the condition.
Though no cure exists for ADHD, symptoms usually can be managed
with medications and behavioral interventions, according to
Michael L. Cuccaro, an associate professor in the department of
human genetics at the Hussman Institute for Human Genomics at the
University of Miami Miller School of Medicine, said he was not
surprised by the finding. "We are moving in a direction where CNVs
are playing a role in a number of different neurobehavioral
conditions," Cuccaro said.
CNVs are important in disrupting pathways that could cause
mental problems, he explained. "A CNV in the same location could
give rise to any number of different conditions," he said.
Cuccaro said he doesn't think a given CNV is specific to ADHD
but rather that the effects of a CNV are more likely to result in
ADHD plus intellectual disability. "A lot of things can go wrong
when you have a CNV," he said.
And, he said, knowing the genetic landscape that can predispose
someone to ADHD or another developmental condition could eventually
become useful in diagnosing the conditions.
Knowing the genetics involved in ADHD also might lead to new
treatments, as well as making current treatments more effective,
The U.S. National Institute of Mental Health has more on
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