The Genetics of ADHD

January 30th, 2013 | Add a Comment

Attention deficit-hyperactive disorder (ADHD) is the most common psychiatric disorder among children. Approximately 8 to 12 percent of the infant-to-adolescent population worldwide suffers from ADHD, and about 50 percent of these ADHD cases persist into adulthood. Despite these numbers, there is still no official tool to diagnose ADHD.

The symptoms of ADHD include difficulty paying attention, being frequently distracted, and having difficulty completing tasks. Some people with ADHD also display impulsive behavior and engage in excessive, inappropriate activities. It is very challenging for individuals with ADHD to contain their impulses.

In a provocative new thesis, researcher Alaitz Molano of Spain’s UPV/EHU-University of the Basque Country, attempted to fill the inconsistent diagnosing gap by not only identifying a way to improve the diagnosis of ADHD but also to enhance the current treatments.

Molano chose this topic to research because she feels ADHD has a big impact on society. She says, “All these [ADHD] symptoms seriously affect the social, academic and working life of the individuals, and impact greatly upon their families and milieu close to them.”

Molano and researchers collected around 400 saliva samples from patients with ADHD along with 400 samples from healthy individuals without a history of psychiatric diseases. The researchers narrowed the genetic foundation from over 250 DNA polymorphisms, or variations, to uncover 32 polymorphisms associated with both the diagnosis of ADHD and the evolution of the disorder.

Molano stated, “We looked for all the [genetic] 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.”

The study also confirmed the existence of the three known subclasses of ADHD: lack of attention, hyperactivity, and a combination of the two. “It can be seen that on the basis of genetics the children that belong to one subtype or another are different,” Molano said.

However, the genetic analysis was unable to establish a direct association between the polymorphisms and the patient’s response to pharmacological treatment. Molano said this might be due to the difficulty in collecting pharmacological data, adding that “in many cases the data on drugs we had available were not rigorous.”

Molano said that her future studies will focus more on resolving the current lack of understanding regarding the genetic mechanisms behind ADHD drug interactions.

“We want to concentrate on the drug response aspect, obtain more, better characterized samples, and monitor the variables in the taking of drugs very closely, whether they were actually being taken or not, etc.,” she said.

Molano said that she hopes this study will lead to better diagnostic tools and a better outcome for those diagnosed with the condition.

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