Autism Clusters Tied to College-Educated Parents

Highly educated parents may be more likely to have children diagnosed with autism, according to a recent study from the University of California at Davis.

The findings suggest a new, major risk factor for this complex, and still mysterious, developmental disability.

Dr. Karla Van Meter, the lead author for the study published online this month in the journal Autism Research, and her colleagues examined the birth records for 2.4 million live births that took place in California between 1996 and 2000.

After mapping the physical residences at the time of delivery of the mothers of children who were later diagnosed with autism -- about 10,000 in all -- the researchers examined commonalities among parents.

When education level was factored in, the researchers found 10 population clusters of autism diagnoses.

Clusters are groupings of a population with a common trait that can't be explained by random happenstance. In this case, areas where highly educated people lived had greater rates of autism diagnoses.

Van Meter and her colleagues examined the prevalence of autism inside these education level clusters against the areas just outside. The difference in the rate of autism cases between the two areas was nearly double in some places.

WATCH VIDEO: Take a look at this video from Discovery Health to learn more about autism.

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What's more, the prevalence of autism diagnoses increased along with advancement in education, from parents who didn't graduate high school to parents with a college degree.

There is heavy debate about the causes of the mysterious developmental disorder, often characterized by repetitive behaviors and difficulty with social interactions.

Exposure to pollution, ingredients in inoculations and the advanced age of parents have all been nominated as causes for autism. Van Meter says that while her findings don't rule out other possible causes for the autism clusters, they do strongly favor education as a risk factor for autism.

"There's sort of a steady increase through the four levels of education," she told Discovery News. "That looks a little weird when you view it through chemical exposure as an explanation."

Van Meter says explaining why high levels of education is a risk factor in autism is a difficult proposition. She's cautious to point out that the study results show a correlation, not causation.

Additionally, the education-based clusters don't rule out environmental pollutants. Instead, they show that if such exposure is a cause of autism, parents with higher education levels are more likely to experience these kinds of environmental hazards than those with lower levels of education.

Dr. Peter Gerhardt, president of the scientific council at the Organization for Autism Research, agrees that a cautious approach should be taken when evaluating correlations like the one uncovered by Van Meter's study.

He notes that the results could reveal something as simple as a higher level of autism awareness among highly educated people. "At least in part, the more you are educated, the more you might readily recognize the symptoms of autism and push for a proper diagnosis," Gerhardt told Discovery News.

At this point, autism solidly remains a mystery; explanations of its causes are still very much a guessing game.

Josh Clark is a writer for HowStuffWorks.com.