At the age of 2, Arik Dahlen would first greet a new playmate with an intense stare. Then he would push the child over.
His mother, Kari Dahlen of Lafayette, Calif., noticed other odd behaviors, including language delay, so she spoke to her pediatrician.
"The doctor initially dismissed it," said Dahlen, but a year later Arik unexplainably got on all fours on the examining room floor and began meowing loudly like a cat.
"Suddenly the doctor was overexcited and said, 'Why didn't you talk to me about this earlier?'" said Dahlen. "Clearly this was not normal for a child."
Arik was later diagnosed with PDD-NOS (pervasive development delay, not otherwise specified), a milder form of autism that is grouped among a wide swath of autistic behaviors.
For decades, the incidence of autism in the United States was considered to be about 1 in 2,000 children, according to the Centers for Disease Control and Prevention. Now, using improved methodology, the incidence is believed to be about 1 in 150, a statistic that is even higher for boys — 1 in 94.
"This is a major public health problem, but we are not using the term epidemic," said Marshalyn Yeargin-Allsopp, a CDC pediatrician.
Now a debate is raging over whether the apparent spike in autism is a result of more cases or the inclusion of less severe behaviors like Arik's.
Some doctors say autism advocates have over-reacted, creating new medical pathologies for milder cases of social awkwardness that were once considered a variation of normal.
Nevertheless, medical experts agree that more and early diagnoses are leading to better care for those affected.
This week, the American Academy of Pediatrics released two new reports to help pediatricians recognize autism. Intervention before the age of 3 can dramatically change outcomes, they say.
"Autism definitely makes the list of many parents' top anxieties," said Rebecca Odes, author of "From the Hips" and parent advice columnist for babble.com.
"Parents are left watching and waiting to find out if their child develops any of the symptoms," said Odes. "Many of the warning signs of autism are also common in babies who don't have autism."
Autism is defined by significant impairments in social interaction and communication. Many children have unusual ways of learning, paying attention or reacting to different sensations. Children can range from gifted to severely challenged, according to the Florida State University Center for Autism and Related Disabilities.
The statistics on autism can be misleading when comparing earlier studies in the late 1980s and 1990s, a time when different diagnostic criteria was used, Yeargin-Allsoppa noted.
Now, the CDC uses "active surveillance," rather than just receiving reports, and consistent rubrics to count children.
To put autism in perspective, about half the number of children diagnosed with autism — three in 1,000 — have cerebral palsy. One in 800 has Down syndrome; only 1 in 1,000 has hearing or vision loss. But 9.7 in 1,000 are diagnosed with mental retardation.
Overall, a staggering 17 percent of all children are affected by a large group of learning disabilities, including autistic behaviors. "The impact of this is huge," said Yeargin-Allsoppa.