26 new genes have been identified by the scientists which are linked to intellectual disability in humans. The new discovery may lead to personalised treatments for individuals affected with autism.
Researchers, including those from Queens University in Canada, studied about 192 families from Pakistan and Iran with more than one affected family member.
Intellectual disability is frequently caused by recessive genes, meaning that an affected child gets a defective copy of the gene from each parent, researchers said.
All the families studied had a history of marriage among relatives, which occurs quite commonly in communities in South Asia, the Middle East and Africa.
Studying families with this background and multiple affected individuals enabled researchers to identify disease genes that would otherwise remain hidden.
The team pinpointed mutations related to intellectual disability in half of these 192 families, in 72 different genes.
The identification of 26 new genes adds to 11 new genes that the team had previously linked to intellectual disability, researchers said.
"Theres an opportunity now to further explore the functioning and biological pathways of these genes and to help complete the picture of how the central nervous system works," said John Vincent from Centre for Addiction and Mental Health in Canada.
This discovery may eventually lead to personalised treatments for individuals affected with autism, researchers said.
"Knowing the genes involved is a big step forward, but understanding how they function is also crucial before we can start planning treatments or even cures," Vincent said.
The study was published in the journal Molecular Psychiatry.