Immunizations and Autism
There has been controversy about whether a mercury-based vaccine preservative called thimerosal, or the measles-mumps-rubella (MMR) vaccine, are linked to autism in some children. After intense investigation, multiple respected health organizations, including the American Academy of Pediatrics, the Centers for Disease Control and Prevention and the Institute of Medicine, state that there is no evidence to support a link.
In fact, over the past several years, the Food and Drug Administration has worked with vaccine manufacturers to eliminate thimerosal or reduce its levels to trace amounts in childhood vaccines. Despite this, diagnoses of autism are growing at a rate of 10 to 17 percent per year, according to the Autism Society of America (ASA).
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It's not clear whether autism is becoming more common or people are getting better at recognizing it. Children with autism have differences in the shape of their brain and have an abnormally high level of the neurotransmitter serotonin. There also seems to be a genetic component, because some families have a pattern of developmental disorders. In recent years, several genetic defects that lead to autism spectrum disorders have been identified.