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.
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
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.
In an animal study, the UC Davis team then injected the antibodies into
animals. The animals getting the IgG antibodies from mothers of children with
autism displayed abnormal behavior, while the animals given antibodies from the
mothers of normally developing children did not exhibit abnormal behaviors.
In another study, the UC Davis team found that levels of leptin, a hormone
that plays a role in metabolism and weight, was much higher in children with
autism than in normally developing children, especially if their autism was
early in onset.
Another study, just launched by the CDC and now enrolling children, will
track genetic and environmental factors that may increase risk for ASD.
Called SEED -- the Study to Explore Early Development -- the five-year study
will follow more than 2,000 children at six sites across the U.S., says
Newschaffer of Drexel, a co-principal investigator of the study. Some will have
been diagnosed with ASD, some will have a developmental problem other than ASD,
and a third group will be children without developmental problems.
Researchers will collect a host of genetic and environmental information,
Newschaffer tells WebMD. They will find out about medical and genetic histories
of the children and their parents, exposures during pregnancy to potential
toxins, information about behavior, sleep problems, gastrointestinal problems,
and other facts.
The hope, he says, is to find things that "stand out" -- early
exposure to certain substances, for instance, or certain genetic information or
a specific behavior pattern -- that might turn out to be markers for ASD.