Because of these differences, Wiznitzer thought the study -- published today in the journal Pediatrics -- was a litmus test for general socialization or communication problems among children.
"Whether they truly are the components of autistic spectrum disorder has not been proven in this survey," he said.
However, parents' reaction to the news was only affirmation of their fears and their calls for more research.
"The study shows that the increase in autism is real -- you can't have a genetic epidemic -- there are environmental factors in play," said Rebecca Estepp, national media manager for Talk About Curing Autism (TACA). "This is a national health crisis. ... If you're pregnant right now with a little boy [boys are more likely to be diagnosed], that's terrifying to find out. I don't know how it hasn't been declared a national health emergency."
Whatever the factors behind the jump in the rate of cases, the United States government is taking unprecedented steps to study autism further. This February, the American Recovery and Reinvestment Act (ARRA) funneled more money into scientific research thus giving the National Institute of Mental Health roughly $85 million toward new autism research projects.
"This is not business as usual for us. We were doing this before this paper came out, and we were doing this in recognition that autism was much more in common than any of us had thought," said Dr. Thomas Insel, director of the National Institute of Mental Health (NIMH).
Since the stimulus money only funded two years worth of research, Insel said the NIMH decided to direct extra money toward research with fast turnaround time -- including genomics.
"We're trying to develop new treatments and finding ways in which the environment might affect the genome," Insel said.
Dr. Ari Brown, a pediatrician and author of "Baby 411," also thought genomics held some of the most promise for autism research at the moment.
"We know there are certain genetic defects and chromosomal defects with huge incidence of autism spectrum disorders. We need to be looking at prenatal risk factors and exposures," she said. "I believe the 'hit' to a child's neurodevelopment happens before conception, at conception or shortly afterwards -- that's where the money is."
Courtney Hutchinson contributed to this report