Wednesday, January 09, 2008
Investigating the roots of Autism
What exactly causes autism? That is a question I get as much as any other. Of course, there is no absolute answer, but a study caught my eye and I was wondering what you thought. The study, in the Archives of General Psychiatry (Full Study) examines cases of autism in California since 1999. In that year, as you may know, manufacturers began removing thimerosal - a mercury based preservative - from vaccines. The researchers reasoned that if mercury exposure was a major cause of autism, the number of children with autism should have dropped after thimerosal was removed. (Read more or Watch Video)
That didn't happen. From 2004 to 2007, when exposure to thimerosal dropped significantly for 3- to 5-year-olds, the autism rates continued to go up from 3 in 1,000 to 4 in 1,000. Small numbers, but they still point to an important trend. In investigating this story, we interviewed independent doctors not affiliated with the study and one said, "This very clearly shows autism did not arrive through a vaccine."
There are others, though, who say, "Not so fast." And, there are a couple of important points to make. First off, if you really trace the vaccine, you will find thimerosal wasn't completely off the shelves until 2002 or 2003 according to the National Vaccine Information Center. Also, this particular study doesn't include children under the age of 3, which is obviously an important age group, when it comes to the diagnosis of autism.
We do know that the signs of autism may include no pointing or babbling by the age of 12 months. Not a single word by 16 months and no brief phrases by 24 months. Also, loss of language or social skills may be an indicator. None of these are absolute by any means and are just flags to look for. Still, though, where do you come down on the cause of autism? Still worried about mercury? Any thoughts on whether the causes are environmental, genetic or both?
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