DNA chip for Attention Deficit Hyperactivity Disorder
Is your child like this? 'He does not sit still, he makes you crazy always tapping or moving his leg, he cannot do one thing at a time and he is unable to remain seated at the table during dinner. It's like he's got a motor in him; he doesn't stop talking.' In school you may hear teachers say things like 'he does not listen, he does not pay attention, he loses everything, he is unable to do his own work and he makes so many mistakes'. This could be a case of Attention Deficit Hyperactivity Disorder (ADHD).
ADHD is the most common childhood neuropsychiatric disorder. It is a potentially serious problem; a European survey conducted in 2010 found that children with ADHD are statistically more likely to be afflicted with other impairments on their quality of life than children without ADHD. Yet, despite the warning signs, parents take on average 26.8 months to achieve a diagnosis for their child. One reason is that there is currently no tool to confirm an ADHD diagnosis. However, Spanish researcher Araitz Molano-Bilbao from the the UPV/EHU-University of the Basque Country has come up with an innovation that she believes could improve the rate of diagnosis of this disorder, and open the way to potential new therapeutic treatments.
The prevalence of ADHD is calculated to be between 8 % and 12 % among infant-adolescents worldwide, with 50 % continuing to exhibit symptoms in adult life. Children with ADHD have great difficulty in paying attention and completing assignments, and are frequently distracted. They may also display impulsive behaviour and act inappropriately at times. They may experience greater difficulty in controlling these impulses. 'All these symptoms seriously affect their social, academic and working life of the individuals, and impact greatly upon their families and milieu close to them,' says Molano.
Dr. Molano studied how genetic polymorphisms (variations in the DNA sequence between different individuals) are associated with ADHD. 'We looked for all the associations that had been described previously in the literature worldwide, and did a clinical study to see whether these polymorphisms also occurred in the Spanish population; the reason is that genetic associations vary a lot between some populations and others.'
Around 400 saliva samples of patients with ADHD and a further 400 samples from healthy controls (people without a history of psychiatric diseases) were analysed. The analysis of over 250 polymorphisms led to the discovery that 32 polymorphisms could be associated not only with the diagnosis of ADHD, but also with the evolution of the disorder, the specific ADHD subtype, the severity and the presence of comorbidities (the presence of one or more disorders).
On the basis of these results, Dr. Molano has proposed that a DNA chip with these 32 polymorphisms could be used not only for diagnosing the disorder, but also for calculating genetic susceptibility to different variables, including how well the patient is responding to drugs or the normalisation of symptoms.
The study also confirmed the existence of three distinct ADHD subtypes: lack of attention, hyperactivity, and a combination of both. 'It can be seen that on the basis of genetics, the children that belong to one subtype or another are different,' explains Dr. Molano.
By contrast, no direct associations were found between the polymorphisms analysed and the response to pharmacological treatment (atomoxetine and methylphenidate). Dr. Molano believes that this could be due to the fact that 'in many cases, the data on drugs we had available were not rigorous.' Dr. Molano therefore intends to pursue her research in this field. 'We want to concentrate on the drug response aspect, obtain more, better characterised samples, and monitor the variables in the taking of drugs very closely, whether they were actually being taken or not,' she says.
Dr. Molano hopes that this tool will reach clinics and begin to help children with ADHD.
The project was funded by Progenika Biopharma and the pharmaceutical company JUSTE SAFQ. Already 10 collaborating clinics belonging to public and private centres in Spain are looking into this tool with the aim of marketing it.
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Data Source Provider: Elhuyar Foundation
Document Reference: Based on information from Elhuyar Foundation
Subject Index: Medical biotechnology; Medicine, Health