Researchers Detect New ADHD Genes, Link Them to Autism Susceptibility

Researchers have identified more genes in attention deficit hyperactivity disorder (ADHD) and demonstrated an overlap between some of these genes and those found in autism spectrum disorder (ASD) and other neuropsychiatric conditions.

Researchers used microarrays to study the DNA of 248 unrelated patients with ADHD. They specifically searched for copy number variants (CNVs), insertions or deletions affecting the genes.

“In three of 173 children for whom the DNA of both parents was available, they found spontaneous CNVs, which occur when the parents are not affected and mutations are new to the child. Rare CNVs that were inherited from affected parents were found in 19 of 248 patients,” according to a press release announcing the study, which was released online ahead of print in Science Translational Medicine.

The research team was led by Russell Schachar, MD, senior scientist and psychiatrist at SickKids and professor of psychiatry at the University of Toronto, and Stephen Scherer, PhD, Senior Scientist at SickKids, Director of The Centre for Applied Genomics at SickKids and the McLaughlin Centre at the University of Toronto.

“Within the group of inherited CNVs, the researchers found some of the genes that had previously been identified in other neuropsychiatric conditions, including ASD,” according to the press release. “To explore this overlap, they tested a different group for CNVs. They found that nine of the 349 children in the study, all of whom had previously been diagnosed with ASD, carried CNVs that are related to ADHD and other disorders.”

The findings suggest that some CNVs, which play a causal role in ADHD, demonstrate common susceptibility genes in ADHD, ASD and other neuropsychiatric disorders.

“For the first time, we’ve tested these genetic alterations in ADHD and have a pretty good handle on a couple of decent ADHD candidate genes,” said Scherer. “This is critical, as it gives us confidence in interpreting our results.”

Like ASD, ADHD cases are largely unique, and people carrying the same CNVs can have different symptoms, he says. “It’s not always the same risk. As we’ve seen in autism and other conditions, relatively few of these CNVs repeat in affected individuals.”

Most individuals with ADHD also have at least one other condition, such as anxiety, mood, conduct, or language disorders, and up to 75% of people with ASD also have attention deficits or hyperactivity. “A lot of these associated problems probably arise from the fact that they are sharing genetic risk for different conditions,” said Schachar.

The historical mindset in research has been to define the specific clinical syndrome and explore it, Scherer said. “Researchers don’t tend to look across disorders very often. This method is perhaps one of the most exciting findings in neuropsychiatric genetics and it is really starting to redefine how we think about neuropsychiatric conditions.”

Source

Rare Copy Number Variation Discovery and Cross-Disorder Comparisons Identify Risk Genes for ADHD [Science Translational Medicine]