At first glance, it appears that the number of children with autism is skyrocketing in Montana.

In 1991, eight children were classified as autistic. In 2008, there were 495 autistic children. That’s a 6,000 percent increase in 18 years.

But the numbers are misleading, according to Doug Doty, coordinator of the Office of Public Instruction Montana Autism Education Project.

Doty, who has been an autism specialist since 1994, was the keynote speaker Tuesday at an autism conference sponsored by the Western Montana Comprehensive System for Personnel Development.

About 140 teachers, parents and others who work with autistic children are attending the conference, which continues today at the Red Lion Hotel Kalispell.

In 2008, children with autism made up about 2.8 percent of the children with disabilities in Montana, Doty said. Most of them — 93 percent — live in the state’s nine most populous counties, including Flathead.

The data Doty presented Tuesday dated back to 1991. Before that year, there was no autism category according to federal special education legislation, he explained.

Autistic children were included under the mental retardation category, which has since been renamed cognitive delay.

From 1991 to 1998, following federal guidelines, the state of Montana defined children with autism as those who had shown signs of autism before age 3. Children who had “autistic-like behavior” or who first exhibited symptoms after age 3 weren’t included.

The first year those guidelines were used, the state identified eight autistic children. By 1998, that number had grown to 112.

But Doty cautioned that the growth might not really be an increase in autistic children. It could be that children who had previously been labeled mentally retarded were reclassified as autistic, he said.

In 1997, the federal definition of autism changed, and Montana changed its definition two years later. In 1999, children were called autistic if they were diagnosed before age 3 and only if they had the classic signs of autism, not “autistic-like behavior such as ... Asperger’s disorder.”

“It very, very, very, very specifically said if you have Asperger’s, you are not a kid with autism,” Doty said.

In Asperger’s disorder, a person is socially impaired but typically suffers no significant delays in other developmental areas.

The new definition lasted only one year, when 127 children were classified as autistic. In 2000, the state changed its definition again, this time not excluding children with Asperger’s or “autistic-like” characteristics. The new definition also eliminated the need for diagnosis before age 3.

Under the new definition, the number of children with autism has increased from 165 in 2000 to 495 in 2008.

But there is one more change that took place during that time and affected the numbers, Doty cautioned. In 2001, the state began to include children ages 3 to 5 in its count. Before, it had only counted people ages 6 through 21.

Prior to 2001, children between the ages of 3 and 5 were only considered “children with a disability,” Doty explained.

The numbers have climbed steadily for people ages 6 to 21 over the last nine years, from 165 in 2000 to 441 in 2008.

That growth may be in the number of people diagnosed with Asperger’s, Doty said. He has not had time to delve into researching what is driving the increase, but he points to the relatively flat number of 3- to 5-year-olds diagnosed with autism as evidence.

The number of autistic 3- to 5-year-olds hasn’t changed much since 2005. Because Asperger’s affects social skills and a person’s ability to interact with others, children usually aren’t diagnosed until they reach school age.

The average age for diagnosis is about 11, Doty said. He speculated that perhaps the children in the 3- to 5-year-old category are mostly those with classic autism.

For further information, contact Doty at ddoty@mt.gov.

Reporter Kristi Albertson may be reached at 758-4438 or by e-mail at kalbertson@dailyinterlake.com