`ADHD is a huge risk factor for difficulties and it doesn't go away'
April 30, 2009
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Elaine Carey
SPECIAL TO THE STAR
A child's diagnosis with attention deficit hyperactivity disorder (ADHD) can be devastating for parents. As well as coping with its behavioural effects, they must deal with the fact many people still believe ADHD is the result of poor parenting, not a condition with roots in science.
But ADHD is one of the most common and identifiable psychiatric disorders, characterized by inattention, hyperactivity and impulsiveness. It affects 2 to 3 per cent of school-age children – four times as many boys as girls – and is usually diagnosed by the age of 7.
As well, in the past two decades, scientists have been able to determine that it is one of the most inheritable conditions in psychiatry. Forty per cent of families with an ADHD child have another affected family member.
Exciting research at SickKids is looking at what those possible genetic risks are and what areas of the brain are affected. Right now, they have identified genetic links responsible for 3 per cent of ADHD with eight to 10 different genes seemingly playing a role. As with every other condition, no single gene is responsible.
But controversy about the disorder persists.
"Any condition that exists in children that largely affects their ability and learning is always going to have controversy to it," says Dr. Russell Schachar, a senior scientist in neurosciences and mental health at SickKids.
"But ADHD is as established as any other in psychology and medicine," he explains. "It has established criteria, and clinicians can apply a diagnostic label to the symptoms. We know who to diagnose and how to diagnose it."
That is a remarkable change in a single generation.
"When I was a kid, you were either labelled bad or dumb, there were no kids with special needs," he notes. "Either you were a behaviour problem and you were strapped, or you were shuffled off to vocational training."
But science has come a long way in identifying the causes of ADHD.
While several major studies are going on at SickKids, one, in particular, is looking at the brains of children with ADHD and identifying some of the deficits they have in brain processes.
Pinpointing those deficits is crucial. In at least half of affected children, ADHD persists into adolescence and adulthood and has a serious adverse effect on development. It increases the likelihood teens will underachieve and drop out of school, as well as experiment with drugs and alcohol or become involved in motor vehicle and other accidents.
"ADHD is a huge risk factor for difficulties and it doesn't go away," Schachar says.
While many of these children are being treated with medication and other mental health interventions, they work in only 60 to 80 per cent of cases and are not a cure. There is little evidence they are effective in the long term.
"It doesn't mean they aren't good treatments but they are far from complete," Schachar says. "We believe that instead of trying to tweak current treatments, the way to better treatments is to know more about what's causing the disorders. At the moment, we are using behavioural interventions that are not designed to treat the causes but the overt symptoms."
In one of their studies, Schachar's lab has determined that while children with ADHD have trouble with attention, they don't with all aspects of it and it can vary with tasks. The lab is using functional neuroimaging (fMRI) of the brain to see how ADHD and non-ADHD children differ when performing particular attention tasks. That is allowing them to zero in on atypical brain regions in ADHD.
They are also using these attention deficits to locate genes associated with ADHD by testing children's DNA.
In a unique partnership with the Ontario Science Centre in 2007, SickKids researchers set up a display on brain, genes and attention. Visiting parents completed a questionnaire about their child's behaviour while the child performed attention tasks and provided a DNA sample by spitting. The display collected 850 samples in less than a week and proved to be one of the most popular exhibits in the centre's history.
"Spit for science – people actually groove on that," Schachar says.
This summer, they will set up a similar display from the end of May until Labour Day and hope to collect 10,000 anonymous samples from children and teens, which will allow the lab to compare the genes of children with high levels of certain behaviours with those with low levels.
The large sample size will allow researchers to look at large changes in DNA sequences and show that they run in families, says Dr. Steven Scherer, a senior scientist and director of the centre for applied genomics at SickKids.
There are 25,000 protein-coated genes in the human body and, by the end of this year, they hope to identify a handful that are involved in ADHD.
"Those are very powerful designs to get at the genetic traits of ADHD and we're very excited about that," Schachar says. The cost of trying to set up a similar study without the public's input would be prohibitive."
They hope to take those results and concentrate on the genetic makeup of particular families – although neither they, nor the researchers, will be able to identify them.
In the long run, "spitting for science" may lead to the key to finding targets for treatment of this devastating behavioural condition.
Toronto Star