A new study published in the Journal of the American Medical Association found that autistic children had 67 percent more neurons in the prefrontal cortex and heavier brains compared to typical children.

Scientists at the University of San Diego, partly funded by the National Institutes of Health, arrived at the conclusion by conducting postmortem direct counts of brain cells for seven boys who had autism and six boys who did not.

Most of these participants died in accidents but the researchers did not base their selection on causes of death, according to a press release from the NIH.

Based on their finding, the University of San Diego scientists theorized that autism is associated with faulty prenatal cell birth or maintenance.  Alternatively, it could be caused by a reduction in the naturally programmed death of cells that usually occurs during the third trimester.

This preliminary study is significant for several reasons.

First, it confirms the widely held view that autisms is heavily influenced by prenatal factors.  Before this study, multiple studies also pointed to the genetic causes and heritability of autism.

However, studies have not reliably confirmed any postnatal factors (like vaccines, exposure to drugs, etc.) that would directly cause autism.

Secondly, the study highlights problems in the frontal cortex as the culprit.  The area is involved in the functions of language, social behavior, and attention, which makes sense because these functions match the symptoms of autisms.

A third point stressed by the NIH is that the results were gleaned from rare postmortem tissue of children with autisms.

Efforts to include a larger number of samples are needed to confirm these findings and to identify patterns of age-related changes in autism, stated the NIH.