http://www.time.com/time/health/arti...0.html?cnn=yes

The week also brought a more definitive, though less splashy finding on the causes of autism, published in the Proceedings of the National Academy of Science. A team led by Levitt found that a fairly common gene variation — one that's present in 47% of the population — is associated with an increased risk of autism. People with two copies of the gene have twice the average risk of autism; those with one copy face a slightly increased risk. The gene is intriguing because it codes for a protein that's active not only in the brain — the organ most affected by autism — but also in the immune system and the gastrointestinal tract, two systems that function poorly in many people with autism. Levitt estimates that anywhere from five to 20 genes may underlie the vulnerability to autism. There are probably many routes to the disorder, involving diverse combinations of genes and noxious environmental influences. Could Teletubbies be one of them? Conceivably, but more likely the trouble starts way before TV watching begins.