No easy answers on autism

St. Louis Post Dispatch: To the parents of a young child who suddenly starts to regress, retreat into himself and tune out the world, autism is a devastating diagnosis. Stricken parents naturally wonder why it happened and what can be done about it. But there is scant comfort in the answers from most doctors: "We don't know."
Autism is diagnosed more frequently today than it was a few decades ago. Why? Doctors are more aware of the disorder, which can vary dramatically from what appears to be social awkwardness and learning disabilities to repetitive or physically harmful behavior. But the numbers also seem to be the result of a real increase in autism cases.
Genetics plays a role, but how much of a role is disputed. Some people think genetically predisposed children become autistic when exposed to some environmental toxin. With increasing stridency, they have blamed vaccines, especially vaccines made with a mercury-based preservative called thimerosal.
Vaccines
A 1998 study, which described a dozen children with developmental disorders who also had gastrointestinal symptoms, is often cited by those who give credence to the putative link between autism and vaccines. Eight of the children in that study first had symptoms after receiving a combined vaccine for measles, mumps and rubella.
But last week, the highly respected Institute of Medicine, part of the National Academies of Science, rejected that link. The studies cited by supporters do not demonstrate a cause-and-effect relationship, the institute concluded. In fact, the evidence shows neither vaccines nor thimerosal is the cause of autism. Large-scale studies conducted in the United States and abroad consistently show no relationship between autism and the MMR vaccine. And they show no difference in autism rates among kids who got shots with high levels of thimerosal and those getting shots with very little of the preservative.
Despite those findings, many parents of autistic children remain unconvinced. The same day the government report was released, a group of parents from Springfield, Mo., held a news conference to push a ban on thimerosal in vaccines.
It's easy to understand the appeal of the vaccine theories to the parents desperate for answers -- and someone or something to blame -- for their child's autism. But it's crucial to keep in mind the enormous public health benefits of immunization, which are far from theoretical. What the new institute study suggests is that the search for the root cause of autism must continue down other paths.