Attention Deficit Hyperactivity Disorder (ADHD) is the most common childhood neuropsychiatric disorder. Yet there is currently no tool that will confirm the diagnosis of ADHD. In her thesis entitled "Development of a genotyping system to be applied in Attention Deficit Hyperactivity Disorder and its Pharmacogenetics" ("Desarrollo de un sistema de genotipado para la aplicación en el 'trastorno por déficit de atención con hiperactividad' y su farmacogenética"), the researcher Alaitz Molano, a graduate in biochemistry and PhD holder in Pharmacology from the UPV/EHU-University of the Basque Country, presents a tool that could improve not only the diagnosis of but also the therapeutics for this disorder.
The prevalence of ADHD is between 8% and 12% among the infant-adolescent population worldwide, and 50% continue with the symptoms into adult life. Children with ADHD have difficulty paying attention, do not complete the tasks they have been assigned and are frequently distracted. They may also display impulsive behaviour and excessive, inappropriate activity in the context they find themselves in, and experience great difficulty restraining their impulses. "All these symptoms seriously affect the social, academic and working life of the individuals, and impact greatly upon their families and milieu close to them," says Molano.
In view of the problems existing in diagnosing ADHD patients and deciding about their treatment, this PhD thesis set out to develop and clinically validate a genotyping tool that could help to confirm the diagnosis, to predict how it will evolve, and to select the most suitable pharmacological treatment in each case.
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."
About 400 saliva samples of patients with ADHD and a further 400 samples from healthy controls without a history of psychiatric diseases were analysed. And the use of over 250 polymorphisms led to the discovery of 32 polymorphisms associated not only with the diagnosis of ADHD but also with the evolution of the disorder, with the ADHD subtype, the symptomatological severity and the presence of comorbidities.