For the first time, researchers have discovered genetic variations that are related to ADHD. For this research, an international consortium of scientists collected genetic material from no fewer than 20,000 patients and 35,000 healthy subjects. Professor Barbara Franke (Radboud university medical center), leader of the ADHD branch of the consortium, was involved in the research.

Worldwide, about 5 per cent of all children and 2.5 per cent of adults have ADHD (attention deficit hyperactivity disorder). The strong hereditary link of the disorder was already known. ‘What we didn’t know was which genetic variations that were at the root of it’, says Franke. ‘We have now discovered twelve really important locations on the genome. These are only twelve of perhaps thousands, so it’s merely the tip of the iceberg, but it certainly is a very important start.’

Why is it important to locate these genetic variations?

‘Knowing which genetic variations play a role helps us to understand the biological processes behind ADHD. We think that the thousands of ADHD-related genetic variations together influence several dozen processes, which in turn influence behaviour.’

Can you name an example of such a biological process?

‘For example, there are strong indications that the development of neurons during the development of the brain is different in people with ADHD. Also, certain neurotransmitters – the substances that transmit messages in the brain – seem to work differently in people with the disorder.’

If you knew which biological processes cause ADHD, could you also intervene, i.e. cure ADHD?

‘Eventually, you hope to develop a better therapy. At the moment, treatments are mostly focussed on suppressing symptoms. Moreover, all the medicines we use for this were discovered by accident. What we want, is to use an evidence-based approach for the treatment of ADHD: trying to figure out which processes malfunction in this disorder, and then develop medication or therapies that are based on that evidence.’

Could genetic knowledge also contribute to the diagnosis of ADHD?

‘At the moment, we lack the knowledge to use that information. However, ultimately, we do want to be able to support the psychiatrist with a biological test. You could use genetics to perform this test. The problem is that the genetic predisposition to ADHD is related to many other disorders: depression, addiction, autism, you name it. At most, a genetic test can be used to say that someone has an increased risk of a disorder. The psychiatrist has to determine which disorder this is.’

‘Patients tell us that the research is important to them.’

You say ADHD is an emotionally charged subject. Why is that exactly?
‘Some people think you shouldn’t label children with a disorder because that label will stay with them for the rest of their life. Although there is some truth in that, we know that children are better off if they receive some form of treatment. Moreover, our current society requires that label to ensure treatment.’

‘On the other hand, there are those who do not believe that ADHD exists. They think of these children as ‘being intentionally difficult’ or that they were not raised well.’

Does your research contribute to recognition for those children and parents?
‘It certainly contributes, especially if we can locate the biological processes. Last year, we researched ADHD in the brain, and that research also demonstrated some differences between people with and without ADHD.’

‘Patients and patient organisations frequently tell us that the research is important to them. It gives them the support needed to say: “My child has an actual disorder and is not just ‘being difficult'”.’