Harvard researchers looked at the genetic makeup of large Middle Eastern families in search for clues regarding autism. The traditional Arab families were chosen because marriages between cousins make it much more likely that rare mutations will be expressed. Furthermore, Middle Easterners have many more children than Western families have, which also helps genetic studies.

The study, by a team led by Howard Hughes Medical Institute investigator Christopher Walsh, involved visits in Turkey, Dubai, Kuwait and Saudi Arabia, in order to verify autism diagnostics and ensure the accuracy of the results.

It appears that autism is caused by the deletion of some genes and turning off of other genes, which cause disruptions in the brain's ability to form new connections in response to experience. This means that autism may fundamentally amount to molecular defects in learning.

There are good and bad news. The bad news is that there appear to be hundreds of genes involved in autism, most or all of which control the brain's learning processes. The good news is that most of the affected genes will be treatable in the future, because turning genes on and off is something considered doable in the future.

It is still unclear what the cause for autism is, but a combined cause with a large genetic component is suspected. People affected by the disorder are characterized by social impairments and often lack the intuition about others that many people take for granted. Autism Spectrum Disorders are associated with periods of severe tantrums and one third of autistic children also have displayed aggression, especially when the disorder is associated with mental retardation (as it often happens).

Last month, a new study by the U.S. Centers for Disease Control and Prevention published in the June edition of the journal Pediatrics revealed that infants born before term and underweight, especially baby-girls are twice as likely to develop autism.

The analysis showed that baby girls weighing less than 5.5 pounds had 3.5 times increased risk of autism. Also, prematurity seemed to influence, as baby girls born more than seven weeks early had a 5.4 times increased risk of autism. For boys, the birth weight and prematurity didn’t have a significant difference in their risk of being autistic.

The findings suggest that, even though autism is partly genetic, partly caused by environment factors, boys and girls appear to have different risk factors for the disorder.