WEDNESDAY, May 18 (HealthDay News) -- More children aged 3 and younger are now being treated for autism in Massachusetts, a new study finds.

One in 129 children in Massachusetts born between 2001 and 2005 was enrolled in early intervention programs for an autism spectrum disorder by their third birthday, according to the study.

Over the five-year period, the proportion of children aged 3 and younger getting treated rose from one in 178 among children born in 2001 to one in 108 for those born in 2005 -- a 66 percent increase.

Much of the increase in diagnosis occurred among boys, which increased by 72 percent from 2001 to 2005, compared to about 39 percent among girls, the investigators found.

The study authors said they aren't sure if the reason for the rise is because greater awareness and better availability of services means kids are getting diagnosed and into treatment sooner, or if autism itself is becoming more common.

"We are showing an increase in diagnoses in autism, and there are multiple things that could be contributing to that," said study author Dr. Susan Manning, who was a maternal and child health epidemiologist at the Massachusetts Department of Public Health at the time the research was conducted.

Those factors could include efforts by the state department of public health to promote early identification and referral of children with autism spectrum disorders, national efforts to promote autism screening such as the U.S. Centers for Disease Control and Prevention's "Learn the Signs, Act Early" campaign, and media coverage that's resulted in increased public awareness.

"A certain portion of the increase could be due to an actual increase in autism," Manning said.

The Massachusetts numbers, Manning noted, are comparable to estimates from the U.S. Centers for Disease Control and Prevention for older kids, which put the number of 8-year-olds with autism at one in 110, while another study found that one in 91 children aged 3 to 17 has autism. And a recent study from South Korean researchers found an estimated one in 38 South Korean children -- or 2.6 percent -- has an autism spectrum disorder.

Other experts said the study likely reflects an increase in kids under age 3 getting help for autism, not an increase in prevalence.

Researchers relied on data from birth certificates and on children enrolled in early intervention programs for autism. In 1998, Massachusetts established the Early Intervention Specialty Services Program for kids with autism, which offers free intensive programs for young children who screen positive for autism spectrum disorders.

While the screening checklist is helpful in determine who might have autism, it isn't a definitive diagnosis, said Irva Hertz-Picciotto, deputy director of the MIND Institute (Medical Investigation of Neurodevelopmental Disorders) at University of California, Davis.

"The paper is most useful for assessing utilization of services and health planning, and is just plain not comparable to estimates from, say the CDC's ADDM [Autism and Developmental Disabilities Monitoring] Network," Hertz-Picciotto said.

The study was released online May 16 in advance of publication in the June print issue of the journal Pediatrics.

According to background information in the article, the average age of diagnosis for autism remains at 3.5 to 5 years old.

The paper seems to show that kids in Massachusetts at least are beginning to get diagnosed and into treatment sooner -- good news, said Dr. Rebecca Landa, director of the Center for Autism & Related Disorders at Kennedy Krieger Institute.

"This paper highlights the fact that more children are getting autism spectrum disorder services," Landa said. "All those working hard to identify these early signs of autism spectrum disorder and promote the fact that early intervention helps, that's starting to have a public impact."

In 2001, white children were more likely to be diagnosed with autism than black or Hispanic children. However, by 2005, those disparities had largely disappeared, perhaps because of outreach efforts specifically targeted at minorities, Manning said.

Infants younger than 24 months of age whose mothers' primary language was not English or were foreign-born were less likely to be diagnosed with autism.

Boys were from four to five times more likely to be diagnosed with an autism spectrum disorder than girls, the researchers found.

"We're really trying to highlight the importance of early diagnosis and getting children into intensive services early," Manning said.

Autism is a neurodevelopmental disorder that's characterized by problems with social interaction, verbal and nonverbal communication, and restricted interests and behaviors.

More information

The U.S. National Institute of Neurological Disorders and Stroke has more on autism.