Researchers from the Broad Institute in the US and Danish iPSYCH project have discovered the first common genetic risk variants for autism and uncovered genetic differences in clinical subgroups of autism. The finding will enable scientists in future to better determine the genes which separate the diagnostic groups and make more precise diagnoses.

The study compared the genomes of 20,415 individuals with autism with 174,280 healthy control subjects, and led to the identification of five different genetic variants which increase the risk of autism.

The researchers also found a considerable overlap between the genetic background for autism and other mental diseases including depression and schizophrenia. It also had links with positive traits, however, including educational attainment and IQ.

According to Professor Mark Daly from the Broad Institute, autism has a heredity factor of up to 80%: “so genes have a great deal of impact overall. Nevertheless, despite many years of work, identifying precisely which genes are involved has been very challenging.”

Associate Professor Jakob Grove of Aarhus University added that: “It is known that there are very rare genetic variants that carry a high risk for autism, but they do not explain many cases. However, according to our estimates, there are common variants that do that when enough of them act together.

“In this study we have examined all the approximately nine million frequent variants that can be found in the genome of the people who are included in our study. These are genetic variants which are common in the population at large and where the individual variant’s contribution to the risk is very small.”