New Research Identifies Genetic Variants Linked Separately to ADHD and Autism Speech Issues

Scientists from a consortium of prominent research institutions studied the entire genomes of more than 20,000 people with attention deficit/hyperactivity disorder (ADHD) and compared them to the genomes of 35,000 who did not have ADHD. They identified 12 genetic variants in the ADHD group, suggesting an increased risk of ADHD compared to those without the variants.

The consortium has researchers from the Danish iPSYCH project, the Broad Institute of Harvard University and the Massachusetts Institute of Technology, Massachusetts General Hospital, SUNY Upstate Medical University, and the Psychiatric Genomics Consortium. The research was published in the journal Nature Genetics.

ADHD is considered a highly heritable childhood behavioral disorder. It affects about 5 percent of children and 2.5 percent of adults. Research has suggested that genetic factors play about 75 percent of the risk for 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,” stated Ditte Demontis, associate professor with Aarhus University in Denmark, and co-lead author of the study. “The search for such genetic risk variants for ADHD has spanned decades but without obtaining robust results.”

Demontis went on to say, “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 two-thirds of the total international study sample.”

The variants identified are widespread in the overall population. However, the more you have, the higher the tendency towards AHDH-like characteristics, as well as a higher risk of developing ADHD.

Demontis added, “We also studied the genetic overlap with other diseases and traits. Through this we found a strong negative genetic correlation between ADHD and education. This means that on average genetic variants which increase the risk of ADHD also influence performance in the education system negatively for people in the general population who carry these variants without having ADHD.”

The research also found a positive connection between ADHD and obesity, increased BMI and Type 2 diabetes. In other words, the variants that increase ADHD risk also increase the risk of being overweight and having Type 2 diabetes.

Earlier this week an international team of researchers led by the University of Cyprus and University of California, San Diego (UCSD) School of Medicine identified large-scale association between molecular gene expression activity in blood leukocyte cells and altered neural response to speech in toddlers diagnosed with autism. Their work was published in the journal Nature Neuroscience.

This research measured neural response to speech using functional magnetic resonance imaging (fMRI). They also found an association with a number of genes expressed in blood samples.

“Many of the genes involved are known from other work to be involved in prenatal brain development are human-specific, are linked to vocal learning, and importantly, have been directly implicated in ASD by other genetic and postmortem studies,” stated lead author Michael Lombardo, assistant professor of psychology at the University of Cyprus. “The findings show that different molecular biological mechanisms underpin functional brain development in a subtype of ASD toddlers with poor language outcome, and this biology is present before such outcomes are known.”

The researchers noted that language development in autistic children is very variable. It has largely been unknown if this variation is linked to subtypes of autism. The results of this study suggest there are genetic variations linked to this variability.

“If we can understand that biology,” stated co-senior author Eric Courchesne, professor of neurosciences at UC San Diego School of Medicine, “this may have high impact in future work examining how to best facilitate change to the biology that can then substantially improve longer term outcomes for patients.”