Researchers with the Autism Center of the University of Washington report they are closer to identifying the gene that causes autism. In a study published in the journal Molecular Psychiatry, scientists analyzed DNA samples from 169 families. Each family had two siblings with autism. Lead author Gerard Schellenberg says researchers were careful to track genes in both parents and children. "The major finding is, first of all, in looking for genes is that we have a couple of locations on different chromosomes that are highly likely places for autism genes to be."

Schellenberg says the finding corresponds with previous studies and gives scientists greater confidence they are closing in on the suspected autism gene. "Another major finding that we thought was very interesting, is that it seems that [there are] different genes for autism for boys and girls and that was a bit surprising for us."

Boys are three times more likely to develop autism as girls.

Experts hope that the research will yield clues to better understand what happens on a cellular level to people with autism. Schellenberg says that knowledge could lead to screening for the gene at birth and earlier intervention. "Iif you have [identified the] genes, then you have molecules. And, if there ever are going to be drugs that treat autism, then the pharmaceutical companies need a target. They need a molecule to target. Hopefully genetics can get them a lot closer to that."

But the mystery is not so easily solved. Four to 6 major genes are thought to be responsible for autism and as many as 20 to 30 others may contribute to a lesser degree.