Research carried out at the Children’s Hospital of Philadelphia suggests that structural genetic variants linked to attention-deficit hyperactivity disorder (ADHD) vary considerably between African Americans and individuals of European origin.
The scientists, led Hakon Hakonarson, M.D., Ph.D., a professor at the Perelman School of Medicine at the University of Pennsylvania and Director of the Center for Applied Genomics, believe this may impact how effective some medications for the disorder are for people of different ethnicities.
“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 Hakonarson.
“Given the large number of African American individuals we have recruited into our studies, whose genomes are fundamentally more complex than those of European ancestry, we wanted to see if comparing the coding and non-coding regions of the genome in those of African American and European ancestry could help us pinpoint areas of focus for future research efforts.”
Structural variants in the genome – which include deletions, duplications, copy-number variants, and insertions, among other structural changes to the DNA – have previously been linked to ADHD. However, earlier studies were largely carried out in Caucasian populations of European origin.
As reported in the journal Scientific Reports, the team found over 40 new structural genomic variants significantly linked to ADHD in this study, as well as confirming a number of genes and mutations linked to the disorder in previous research.
Notably, in the ADHD group there was only around 6% overlap in the genes affected by these variants in African Americans and Caucasians.
In total, the researchers sequenced the genomes of 875 children. The group included 205 individuals with ADHD – 116 African Americans and 89 Caucasians – and 670 controls without ADHD – 408 African Americans and 262 Caucasians.
Almost all the variants discovered (98% or more) were located in non-coding regions of the genome and some of these clustered around areas known to be involved in brain function.
“The inclusion of African Americans, coupled with the study of non-coding regions of the genome, identified several structural variants that warrant further study, as they may impact both susceptibility to ADHD and how patients respond differently to therapeutic intervention,” concluded Hakonarson.