Australian scientists have successfully identified 91 genes, 38 of which are new, linked to autism and other intellectual disabilities, the University of Adelaide said on Tuesday.
Prof. Jozef Gecz, head of neurogenetics at the university's Robinson Research Institute, said the study aimed to better characterize the "genetic architecture" of autism compared to other spectrum disorders, but his team found just eight of the 91 genes were unique to autism.
"There is a growing need to distinguish genes that are more likely to be associated with autism spectrum disorders (ASD) and which ones with intellectual disabilities (ID)," Gecz said in a statement released on Tuesday.
"This research aimed to address some of these difficult questions by looking at a very large, international cohort of 11,730 cases."
He said while ASDs and IDs are often labelled in one group, known as neurodevelopmental disabilities (NDDs), researchers were keen to identify which of the thousands of genes linked to NDDs were unique to either ASDs or IDs.
While Gecz's research uncovered and identified 91 genes, including 38 brand new ones, just eight were found to be unique to autism, which would make it marginally easier to identify the disorder.
"For a small group of genes (25) there was a bias for primary diagnosis of ID or ASD, that is, eight genes were primarily affected in patients with ASD and 17 genes primarily in patients with ID. However, the majority of the 91 genes were affected (mutated) in both groups," he said.
"When patients with mutations in the ASD genes were looked at, these were less likely to have seizures, congenital anomalies or microcephaly. In opposite, they were more like to have macrocephaly, that is, increased brain size, which has previously been associated with some subtypes of autism."
Gecz added that the "majority" (65 percent) of all genes were inherited, meaning "not all of them are sufficient on their own to cause the disease".