The finding, published in the July 11 issue of Science, shows that autism is not only caused by the deletion of some genes but also by turning off other genes. These genes cause disruptions in the brain's ability to form new connections in response to experience.
Scientists chose traditional Muslim families because marriages between cousins make it much more likely that rare mutations will be expressed. Such marriages between first cousins increase the prevalence of neurological birth defects by about 100 percent, scientists say.
The study, carried out by the National Institute of Mental Health (NIMH), not only proves that autism is not just a single disease but can be caused by a range of genetic and environmental factors.
Previous studies have shown that enriched learning environments with extra training can help some children with autism. Researchers now say that by finding affected genes it would be possible to treat them in the future. Also, special guidance and training may help activate pathways in the brain.
According to the CDC, as many as 1 in every 150 children in the United States has autism or a related disorder. Autism is characterized by impaired social interaction, problems with verbal and nonverbal communication, and unusual, repetitive, or severely limited activities and interests.
Experts estimate that three to six children out of every 1,000 will have autism. Males are four times more likely to have autism than females.
