Prior studies have suggested that structural variants of the genome play an important role in ADHD. However, these studies focused mainly on coding regions, or regions of DNA or RNA that code for particular proteins, and were also primarily conducted in people of European ancestry.
“We felt as though prior studies of ADHD from a genomic level were not telling the entire story because of whom they were leaving out and what they were studying,” said [researcher] Hakon Hakonarson.
In addition to confirming several structural variants and target genes associated with ADHD identified in prior studies, the researchers also discovered 40 novel structural variants in patients with ADHD. They identified a cluster of structural variants in the non-coding region of pathways involved in neuronal brain function and highly relevant to the development of ADHD, including gene expression in specific ADHD phenotypes.
There was little overlap (around 6%) in the genes impacted by single nucleotide variants between African American and European ancestry. These differences were especially pronounced in the non-coding structural variants. These variants may also impact how patients respond to medications for ADHD.