It was considered a rare condition 20 years ago, when a diagnosis of autism brought a sense of hopelessness. Now, autism has become the fastest-growing developmental disorder in California -- and in that increase, paradoxically, may lie some promise.

California is seeing autism figures explode, with cases climbing steadily for the last decade. The cost to families, schools and the state to establish programs and hire experts to counsel and educate the autistic is staggering.

The condition largely remains a mystery. No one is sure what causes it or how to treat it, or why autism cases have increased so dramatically. Doctors, parents and teachers labor bit by bit, trying to crack through the walls autism builds.

And in that slow, steady work, answers are gradually emerging around a condition that once seemed an unsolvable puzzle. Major studies are under way around the state on everything from case increases to genetics.

Children are being diagnosed and getting help more quickly, with sometimes dramatic improvement. Autism programs can be found in every Bay Area county. Increasingly, parents with autistic children are moving to Silcon Valley in search of services they don't find at home.

Families with autistic kids who might have once felt compelled to hide the problem now talk about their lives with pride -- and hope.

``It's all I've known for the last 13 years,'' said San Jose resident Jill Walton, who has twin autistic boys, Daniel and Matthew. ``It's definitely emotionally and physically and mentally challenging. And exhausting. But it is also rewarding and an act of love.''

In 1993, the California Department of Developmental Services provided services to 4,911 people diagnosed with autism. Today, there are 17,614; more than seven new cases enter the system daily.

Explanations for the growing caseload vary, touching on everything from the biology of brain development to improved ways of diagnosing developmental disorders. Most of those receiving services are 3 to 13 years old. The condition is four times more prevalent in boys than girls.

According to the Autism Society of America, an estimated 500,000 to 1.5 million Americans are autistic or have a less severe form of autism known as pervasive development disorder.

Rapid growth

But whether they suffer from a ``low'' or ``high'' functioning autism, the disorder is growing at an estimated 10 to 17 percent per year, said Robert Beck, executive director of the Maryland-based autism society. Autism and its associated behaviors have been estimated to occur in as many as 6 out of every 1,000 people, according to the Centers for Disease Control and Prevention.

In the Bay Area, which is served by three regional centers for the developmentally disabled, rising autism rates mirror those figures.

``This is an increase everyone should be alarmed by,'' said Santi Rogers, director of the San Andreas Regional Center, which serves people with developmental disorders in Santa Clara, San Benito, Santa Cruz and Monterey counties. One of 21 regional centers in the state, San Andreas is funded by the Department of Developmental Services.

The personal and social costs of the growing caseload are also rising. On average, Beck said most families can expect to pay $40,000 to $50,000 per year for an autistic individual's treatment, either through insurance or their own pockets.

``It's costing the country about $20 billion a year in the current fiscal period,'' said Beck. Extrapolate that out over the next 10 years, Beck said, and the costs escalate dramatically.

Department of Developmental Services officials say the state costs per individual vary widely -- about $12,000 a year for someone living at home to as much as $160,000 a year for someone living in a state facility.

Onset of disorder

What's behind the disorder is as puzzling as the numbers.

First described in 1943 by Leo Kanner, a psychiatrist at Johns Hopkins University, autism is a complex developmental disorder that affects brain function. It typically appears during the first three years and interferes with reasoning ability, imagination, communication and social interaction. Some people with autism can earn high scores on IQ tests, but are unable to explain a simple idea.

People with the condition may also be prone to repetitive or restricted patterns of behavior, obsessing over one activity or movement. Unlike some other major developmental disorders, motor skills are about average for the most part.

Autism was previously confused with mental retardation, but closer study has helped distinguish the two conditions. Mental retardation is marked by an IQ of 70 or below. Motor skills tend to be delayed, or even impaired in more severe cases.

Autism occurs in a variety of racial, ethnic and social groups. It does not seem to be connected to family income, lifestyle or educational levels.

Children and adults with autism typically have problems in verbal and non-verbal communication. In some cases, they can be aggressive or prone to hurting themselves. Some display repeated body movements, such as rocking.

Search under way

Possible causes abound.

More than one gene -- maybe even more than eight -- may be involved, according to Dr. Bryna Siegel, a University of California-San Francisco psychiatry professor with 30 years of work in autism.

Studies of twins provide some of the best insights. Twins are no more likely to develop autism than other children, but identical twins -- two babies who share the same genes because they arise from a single fertilized egg -- offer a way to tell whether a condition is genetically based, because both will be likely to inherit genetic conditions.

Stanford University's Joachim Hallmayer, an acting associate professor of psychiatry, says studies show that in 75 percent of the cases involving identical twins, both will be diagnosed with autism. That is the case with the Walton twins.

But in fraternal twins -- those who arise from two eggs and do not share identical genes -- the likelihood of both children being autistic is far less. If one is diagnosed as autistic, the chance that the other twin will also be autistic is 3 to 5 percent, said Hallmayer. Those odds are the same for regular siblings.

A separate study at the University of California-Davis on the genetics of autistic individuals is also being conducted and is expected to be completed in five years.

At the University of California-San Diego, researchers have found through brain scans that in the early life of autistic patients, two key areas of the brain -- the cerebrum and cerebellum -- develop abnormally.

``We can then further look into how this overgrowth leads to abnormal function, which leads to abnormal behavior,'' said Dr. Eric Courchesne, professor of neuroscience at UC-San Diego's School of Medicine. ``Then the goal is to figure out what causes it, how to control it and normalize it.''

Still others -- including legions of parents -- contend multiple vaccines like the measles, mumps and rubella shot -- the MMR -- cause brain damage leading to autism.

That theory was proposed by English physician Andrew Wakefield in 1998, after he published a study showing a possible problem with the MMR vaccination and sudden onset of a form of autism in a group of 12 children at about 15 months. While there was no direct evidence of a link, it created a firestorm of controversy.

But other experts, who have questioned Wakefield's studies, say the vaccine theory alone can't be the reason.

``As an epidemiologist, it does not make sense to me,'' said Robert Byrd, an assistant professor of pediatrics at the UC-Davis School of Medicine who is working on a major study about growing autism numbers in the state.

Byrd's study seeks to determine to what extent the actual increase in autism in California can be explained by a change in the criteria used for diagnosis. Or, is it a misclassification of cases of autism as mental retardation? Could it be more autistic children are moving into the state to receive services?

Byrd is addressing these and other questions, and the answers will help researchers like him determine how much of the increase is real.

Another unrelated study, to be published this month in the Journal of Autism and Developmental Disorders, may illuminate the issue.

Funded by the California Birth Defects Monitoring Program, the study included eight successive years of California births from 1987 to 1994. It identified 5,038 children diagnosed with autism, and 11,114 children diagnosed with unexplained mental retardation without autism.

All the children are clients of the Department of Developmental Services and their regional centers.

What researchers found points to broader ways of diagnosing developmental disorders. The results may predict Byrd's: over the eight birth years, the autism rate for children increased from 5.8 to 14.9 per 10,000 -- a change of 9.1 per 10,000. During the same period, the rate of unexplained mental retardation without autism decreased from 28.8 to 19.5 per 10,000 -- a change of 9.3 per 10,000.

``I think what I could say is that improvement in detection may be contributing to this upward increase,'' said Lisa A. Croen, a perinatal epidemiologist with Kaiser Permanente, and the study's lead author.

``There has been a shift in how kids get labeled,'' said Croen. She said her data would suggest that over time, children with the same kind of behaviors in earlier years were given an ``eligibility diagnosis'' of mental retardation. An eligibility diagnosis determines what benefits a child can receive.

Eligible for services

Today, those same children are getting an eligibility diagnosis of autism which moves them into a category to receive specialized state services.

But Ron Huff, senior psychologist for the Department of Developmental Services, said that while the rise may be due to better diagnostics, ``We are just beginning to explore some of the clues related to the cause.''

Parents are encouraged to seek earlier diagnosis. At the Children's Health Council in Palo Alto, psychologist Lori Bond said she is seeing ``many, many more under-3-year-olds'' whose parents are referred to her with the question: Is this autism or just developmental delay?

Earlier diagnosis is key, say experts. ``About 15 years ago, we didn't think there was anything we could do,'' said Byrd. ``A child with autism was an emotional and social death sentence to the family.''

Now, he said, making the diagnosis and getting all children into services early ``may make all the difference in the world for some.''

Jill and Andy Walton believe they would never have seen their sons progress -- Daniel, especially, is more connected to the world around him -- without having pushed for early intervention at age 3.

``The brain is still developing until age 6, so you're able to rewire the brain with intensive therapy,'' said Jill Walton. Without that, she said, the prognosis for the rest of their lives ``would have been grim.''