Autism and ADHD share many symptoms. In fact, up to 80% of people with autism also meet the diagnostic criteria for ADHD. Now, researchers from Denmark’s national psychiatric project, iPSYCH, have found that the similatities between the disorders doesn’t end there. From a comprehensive genetic analysis, they have found that they also share the same genetic mutations.
The researchers were able to notice similarities between ADHD and autism by mapping out both genomes. In particular, they found the overlap when sequencing their exomes, the protein-coding regions of the genome, from dried blood samples taken from heel pricks during routine newborn screenings in Denmark. For the study, they analyzed samples taken from 3,962 people diagnosed with autism, 3,477 with ADHD, 901 with both conditions and 5,002 controls.
During their analysis, the researchers principly focused on truncating mutations in genes that are rarely present in the general population- a key sign that they may be harmful. In doing so, they found that these mutations are 1.4 times more frequent in those with autism and/or ADHD than control subjects. Supporting these findings, similar results were observed in two established cohorts of autistic people in the United States.
Currently, the researchers are creating a list of mutated genes that occur among people with autism, ADHD, or both. So far, the most frequently mutated gene among people with the disorders is known as MAP1A gene. Mutated in 11 people with either or both conditions and none of the control subjects, the gene helps organize the cellular skeleton of neurons.
Anders Børglum, principal investigator at iPSYCH and a professor at Aarhus University said, “We discovered an increased burden of mutations that destroy or severely affect the MAP1A gene in those with ADHD and autism, while very few of the control subjects had such changes in the gene."
Beate St. Pourcain, senior investigator at the Max Planck Institute for Psycholinguistics in Nijmegen added, “This naturally begs the question (of) where the differences in the genetic architectures of (autism) and ADHD lie and whether the distinction between (autism) and ADHD is purely a genetic question after all.”