New research published February 6 in the journal Science points to another possible player in this complex of causes: the interplay of hormones and chemicals affecting the fetus during birth. (See "One Thing We Know About Autism: Vaccines Aren't to Blame.")

In a study led by Yehezkel Ben-Ari of the Mediterranean Institute of Neurobiology in Marseille, France, strains of pregnant mice modeled to give birth to offspring showing autistic behaviors were given a drug to lower their levels of chloride. Their offspring, which would normally have been expected to show signs of the disease, were born with no symptoms of autism.

An earlier study in mice in 2006  showed that oxytocin, a hormone that triggers contractions, also acts