The ABCs of ADHD

Written by Jenny Straiton

Twelve genetic factors identified that increase the risk of developing ADHD.11013

Following a genome wide study of over 20,000 individuals with ADHD and 35,000 without, researchers from the international Psychiatric Genomics Consortium (iPSYCH) have identified a set of genes that are involved in the biological basis of the disorder. The study, recently published in Nature Genetics, found that there are 12 distinct locations that can be labelled as a risk factor for developing ADHD.

“The large amount of data enabled us to find, for the first time, locations in the genome where people with ADHD stand out from those who are healthy. The search for such genetic risk variants for ADHD has spanned decades but without obtaining robust results. This time we really expanded the number of study subjects substantially, increasing the power to obtain conclusive results significantly. In particular, we included a large number from the Danish iPSYCH cohort representing more than 2/3 of the total international study sample,” commented lead author Ditte Demontis of Aarhus University (Denmark).

The genes alone show different properties with some involved in neuronal communication and others important for the process of learning and language development. The affected genes were primarily expressed in the brain. The genes were shown to have a cumulative effect with each variant widespread throughout the population: “The more risk variants you have, the greater your tendency to have ADHD-like characteristics will be as well as your risk of developing ADHD,” explained Anders Børglum (Aarhus University). Those with a smaller number of risk factors showed similar yet muted symptoms to those of ADHD such as inattentiveness and impulsivity.

The study also found many correlations with other disorders, one such being a strong negative correlation between ADHD risk and education. It was showed that the more genetic risk variants and individual had, the worse their academic performance. On the other hand, a positive correlation was found between risk of ADHD and risk of obesity and type-2 diabetes.

“The study is an important foundation for further research into ADHD. We can now target our studies, so we can achieve a deeper understanding of how the risk genes affect the development of ADHD with the aim of ultimately providing better help for people with ADHD,” added Børglum

“Overall, the results show that the risk variants typically regulate how much a gene is expressed, and that the genes affected are primarily expressed in the brain,” concluded Demontis.