A set of 30 inherited recessive genes that play a role in intellectual disability have been identified.
The new findings, published in the online journal Molecular Psychiatry, could be applied to DNA screenings in determining the possibility of a couple producing a child with intellectual disability.
"The implications are enormous," said principal investigator Saima Riazuddin, Professor at University of Maryland School of Medicine in the US.
Intellectual disability, or ID (previously known as mental retardation), becomes apparent in children before the age of 18 and affects, according to the US Centers for Disease Control and Prevention (CDC), as many as 213 million people around the world.
The disorder, which is measured by an intelligence quotient below 70, significantly limits an individual's intellectual ability and practical skills.
The new study presents the outcomes of a five-year investigation that was conducted over three continents.
In order to identify potential genetic causes of intellectual disability, investigators assembled a test group of 121 families in rural Pakistan, in which there was a higher incidence of the disorder and consanguineous marriages (marriages between blood relations).
More than 15,000 DNA samples were collected, which were analyzed both in the Netherlands and at University of Maryland School of Medicine's Institute of Genomic Sciences (IGS), using next-generation genetic sequencing.
From an initial pool of 2,000 possible genes, the study categorized 30 novel candidate genes possessing a strong potential for causing ID -- and possibly other brain disorders as well.