The spike in autism prevalence is apparently not linked to a kind
of mercury once used in childhood vaccines, according to a study in the
journal Pediatrics.
Because autism is often diagnosed around the same time that
children are inoculated against infectious diseases, some parents have
blamed vaccines for triggering the disorder, which is characterized by
impaired communication, repetitive behavior and an inability to relate
emotionally to others. Thimerosal, a mercury-based preservative used in
vaccines, was thought a likely suspect because even small amounts of
mercury can cause neurological damage.
Researchers tallied some three decades of autism cases in Denmark,
which in 1992 was the first country to ban thimerosal. If thimerosal were
to blame in even some cases, researchers hypothesized, they would have
seen some decrease in autism in the late 1990s. Instead, autism diagnoses
continued to rise in Denmark as they have around the globe.
Environmental toxins remain under suspicion, but many scientists
believe the increase in autism diagnoses is due to better recognition of
the disorder’s varied symptoms. Others believe there is a strong
genetic component. Autism is four times more common in boys, but girls
tend to have more severe symptoms.
