Different genes may be responsible for causing autism in boys than in girls, researchers said on Wednesday in a study that may help explain why the condition is more common in boys.
And other genes may play a role in the early onset and late onset forms of autism, the researchers at the University of Washington reported in the journal Molecular Genetics.
These findings could help scientists understand autism at a
molecular level and seek ways to prevent it, Dawson added.
The U.S. Centers for Disease Control and Prevention
estimated in May that autism was very common among U.S.
children -- with up to one in every 175 with the disorder. That
would mean at least 300,000 U.S. schoolchildren have autism, a
condition that causes trouble with learning, socializing and
The researchers examined the DNA of 169 families with at
least two siblings who met the strict criteria for autism.
They also scanned the DNA of 54 other families that had
members with autism and less-severe forms of the disorder, such
as Asperger syndrome.
They came up with "strong support" for an autism gene on
chromosome 7 and "less, but still compelling evidence" for
genes on chromosomes 3, 4 and 11, said Gerard Schellenberg, a
professor of medicine at the University of Washington who led
"It is highly unlikely that there is only one gene
responsible for autism," Schellenberg said in a statement.
"There may be four to six major genes and 20 to 30 others
that might contribute to autism to a lesser degree," he added.
"And because autism is rarer in females, it may take more
risk genes for a female to have autism. There also is the
possibility that there might be a biological difference in
autism for females versus males."
The researchers said they were looking for genes that might
put children at higher risk of autism so they could begin early
treatment or perhaps even one day find a way to prevent the
"Once we discover these susceptibility genes, we can
immediately screen infants to identify those at risk early in
life. Early identification can lead to early intervention,
which could have a much more dramatic effect," Dawson said.
"Also, when a gene is discovered, you discover the
underlying biology of autism at the molecular level. Once you
understand the biology you can develop a prevention strategy
including medical approaches," Dawson said.