Researchers have pinpointed 10 geographic areas in California with elevated rates of children diagnosed with autism. And every one of those "autism clusters" also has an above-average number of parents who hold university and college degrees.
Does that mean well-educated folks are more likely to give birth to an autistic child?
Not necessarily, says the study's lead author, Karla Van Meter, who conducted the research while working on her PhD at the University of California, Davis.
She said it's also possible that parents with lower education levels are less likely to seek professional help if their children show early signs of developmental problems. As a result, potential cases of autism may go unreported among their kids, or are not diagnosed until a later age.
"I think obviously, if you are more educated, you are going to be more successful at negotiating and dealing with the government to get services," said Dr. Van Meter, who is now an epidemiologist with the Department of Public Health in Sonoma County. "But there might be something else going on," she acknowledged. "We just don't know."
Indeed, in recent years numerous hypotheses have been put forward to explain the apparent rise of autism, a spectrum of diseases ranging from severe to mild impairments in social interactions. Children with autism often engage in repetitive and solitary activities.
One provocative theory, dubbed the "Geek Syndrome," holds that smart but socially awkward individuals are attracted to one another and produce children of a similar disposition.
The new findings are based on data from the California Department of Developmental Services, which provides financial assistance to families who need extra help raising a child with autism and related disorders.
The original goal of the study was to look for environmental factors that might contribute to the development of autism. The researchers first set out to find clusters of cases. Over all, they charted the location of about 10,000 autistic children born between 1996 and 2000.
From that analysis, they isolated 10 hot spots in the state where the incidence is significantly higher than in surrounding areas.
When they then examined demographic information for those pockets, one fact stood out above all others: "It turns out all the clusters we found were also significantly associated with highly educated parents," Dr. Van Meter said.
She added that environmental factors could still be playing a role.
But looking at autism clusters in California is unlikely to provide worthwhile clues because the link to higher education seems to overshadow other potential risk factors.
By contrast, in Denmark, where residents have access to universal health care, a child's chance of being diagnosed with autism is not tied to the education level of parents, earlier studies have shown.
"In the end, it could be a little bit of everything [that leads to autism]" said Dr. Van Meter, whose study was published in the journal Autism Research.
"There may be a tendency towards autism within a family and then some environmental trigger pushes a child further in that direction."