Scientists find potential genetic link to ADHD
New research has identified 12 DNA segments that may raise the risk of developing attention deficit hyperactivity disorder (ADHD).
The work, published in the journal Nature Genetics, revealed that researchers have conducted a large genetic analysis of the condition reportedly affects around 6 million children in the US alone.
Benjamin M. Neale from Harvard Medical School, Anders D. Børglum from Aarhus University in Denmark, and Stephen V. Faraone from the State University of New York led the international team working on this research.
As the authors explain in their paper, ADHD is a highly heritable childhood behavioral disorder that affects 5% of children in the US but also 2.5% of adults.
As a heritable disorder, there are numerous genetic variants that raise the risk of ADHD. Although researchers believe that 74% of ADHD risk is genetic, they have not yet firmly linked any genes with the disorder.
Therefore, Neale’s team set out to examine the genome of over 50,000 people across the globe, including more than 20,000 people with an ADHD diagnosis. In total, they analysed about 10 million genetic loci.
Study co-author Bru Cormand, who is also the head of the Research Group on Neurogenetics at the University of Barcelona in Spain, says that the team found common genetic variants, called single nucleotide polymorphisms (SNPs), that account for 21% of the total ADHD genetics.
“Most genetic alterations that were identified are found in regions of the genome that have remained throughout evolution, which highlights their functional relevance,” Cormand continued.
Specifically, the researchers identified 12 genomic segments that could make a person susceptible to ADHD. Many of the genetic changes that ADHD involves affect the expression of certain genes in the brain, say the researchers.
For instance, one of the DNA fragments corresponds to FOXP2 – a gene that plays a key role in human language development. FOXP2 encodes a protein that helps create neural synapses and thus facilitates learning.
The study found a second gene called DUSP6. This gene contributes to the regulation of dopamine, a neurotransmitter that makes learning possible.
Finally, the researchers also identified the SEMA6D gene as one that seems to raise ADHD risk. SEMA6D expression occurs during the development of the embryo, and some researchers believe that it helps develop neural branches.
Overall, the study found that ADHD shares a genetic background with several other psychiatric and non-psychiatric conditions.
“This study reinforces the idea that ADHD is a disorder with a solid biological basis, where genetics means a lot,” adds the author.
This study is the first to start identifying the specific genes that relate to ADHD risk.
“These results show the importance of promoting large scale-studies – which are only possible through big international consortiums – to explore the genetic basis of complex brain diseases,” explained Cormund.
