Autism Cases on the Rise; Reason for Increase a Mystery
Scientists are scouring genetic and evironmental data to find a cause for the rise in autism.
Zeroing in on Environmental Triggers continued...
Another toxin to the brain is mercury in its organic form. But according to a report published in Pediatrics, there is no evidence that children with autism in the U.S. have increased mercury concentrations or environmental exposures. Though many parents of children with ASD believe their child's condition was caused by vaccines that used to contain thimerosal (a mercury-containing preservative), the Institute of Medicine concludes there is no causal association.
Even so, many autism organizations remain convinced there is a link. The vaccine-autism debate reignited in early March 2008, after federal officials conceded to award compensation to the family of a 9-year-old Georgia girl who developed autism-like symptoms as a toddler after getting routine childhood vaccinations. Officials said the childhood vaccines given to the girl in 2000, before thimerosal was phased out, aggravated a pre-existing condition that then manifested as autism-like symptoms. The pre-existing condition was a disorder of the mitochondria, the "power sources" of the cell, according to the family.
Tracking the Genetic-Environmental Interplay
More answers are coming. Pessah of UC Davis is one of the researchers in the CHARGE Study (Childhood Autism Risks from Genetics and the Environment), an ongoing study of 2,000 children. Some of the children have autism, some have developmental delay but not autism, and some are children without developmental delays.
Pessah and other researchers are focusing on how the interaction of genes and the environment play a role in autism.
Among the findings so far, he says, is that the immune system functioning of the mother may play a role in the child's later development of autism. Pessah and his colleagues took blood samples from 163 mothers in the CHARGE study -- 61 had children with autism, 62 had normally developing children, and 40 had children with non-autistic developmental delays. Then they isolated immune system antibodies, called IgG, from the blood of all the mothers. They took the blood samples and exposed them in the laboratory to fetal brain tissue obtained from a tissue bank.
Antibodies from the mothers of children with autism were more likely than antibodies from the other two groups to react to the fetal brain tissue, Pessah says, and there was a unique pattern to the reaction.