A new genetic analysis of people with autism and their relatives has uncovered 18 genes associated with the disorder.
People with autism often had dozens of mutations that may have caused their symptoms — an average of 73 unique mutations, the team at Autism Speaks found.
Some of the mutations might be affected by medications, the researchers reported in the journal Nature Neuroscience.
The study adds to the considerable evidence that autism is a condition caused by genetics, and also adds to a growing body of evidence that each person with autism has his or her own pattern of DNA changes.
“It’s noteworthy that we’re still finding new autism genes, let alone 18 of them, after a decade of intense focus,” said Mathew Pletcher, vice president for genomic discovery at Autism Speaks.
“With each new gene discovery, we’re able to explain more cases of autism, each with its own set of behavioural effects and many with associated medical concerns.”
Dr Stephen Scherer of Toronto’s Hospital for Sick Children and colleagues studied the DNA of more than 5,000 people in 2,066 families with children diagnosed with autism spectrum disorders, including 2,600 affected children.
They did what’s known as a genome-wide association study — a deep dive looking at all the DNA in a person’s cells, and how it’s different from another person’s.
The 18 genes they identified have not been previously linked with autism, but they are all involved in brain cell communications. There are many different mutations affecting the genes, the researchers said.
There are also genetic changes that don’t affect genes, but that are found in stretches of DNA — once called junk DNA — that affect the activation of genes.
“In fact, the genetic predisposition toward autism spectrum disorder may be different for almost every individual,” the team wrote.