California’s surging rates of autism are real and cannot be explained by heightened awareness of the disorder, population shifts or looser diagnostic criteria, a major new study has found.
The $1 million study was undertaken by the University of California, Davis, at the request of the state Legislature after a 1999 report documented a 273 percent increase in autism rates between the years 1987 and 1998. While autism was once considered a rare condition, affecting one in 2,500 children, recent estimates put the prevalence at one in 500, and sometimes higher.
While the UC Davis study does not provide clues to the cause or causes of autism, it should give increased impetus to finding them, researchers concluded.
“The numbers don’t appear to be artificial,” said Dr. Robert Byrd, the pediatrician and epidemiologist who led the research team at the university’s MIND Institute. “And they challenge our understanding of autism as primarily a genetic condition. It should be concerning for all of us.”
The much-anticipated study also is certain to shake up the neurodevelopmental research world, which has been divided over the possible reasons for increasing rates of the disorder documented in several states and in the United Kingdom.
Eric Frombonne, a psychiatrist and leading autism expert at McGill University in Montreal, for example, has maintained that the rise in autism cases is due to wider recognition of the condition.
The report released Thursday is giving parents and others in the field a sense of vindication about their long-held concerns.
“Those who have simply refused to believe that we are in the midst of a real autism epidemic no longer can put forth their simplistic explanations and denials,” said Rick Rollens, a catalyst for the state’s scrutiny of the burgeoning caseload who is convinced that his 12-year-old son is autistic because of vaccines he received as an infant.
The news also is being used as a call to arms for additional research into possible environmental reasons for the trend.
“My hope is this would be the beginning of serious federal investigation, at a funding level no private foundation can afford,” added Portia Iversen, vice president of the Cure Autism Now Foundation in Los Angeles. “It’s a major health issue. It’s gigantic.”
Autism is a neuro-developmental disorder that affects a person’s ability to speak, relate to other people and respond appropriately to things in the environment. Some people with autism also exhibit odd motor movements such as hand-flapping or rocking.
Many parents report that their child’s symptoms surfaced after years of normal development, suggesting an environmental trigger for the disorder.
Byrd and his team examined the cases of 684 California children covered by one of the state’s 21 regional centers, which evaluate and coordinate services for clients with autism and other developmental disorders.
The children were divided into two groups: the younger group included children born between 1993 and 1995; the older group, children born between 1983 and 1985.
After examining parent surveys, medical charts and past autism assessments of the children in both groups, researchers determined that the criteria used to diagnose autism had not changed in the intervening years.
In both groups of children, Byrd said, the diagnosis given was accurate nearly 90 percent of the time when held up against the criteria established by the American Psychiatric Association, he said.
Byrd also looked at whether migration of families with autistic children to California from other states might be responsible for the increase. He found that about 90 percent of all the children surveyed were born in California.
Only 10 percent of the increase in cases could be attributed to an overall population increase in the state, he said.
Researchers also delved into the thorny issue of misdiagnosis to determine whether children with autism had been misclassified in the past as having mental retardation.
Byrd found that 18 percent to 19 percent of children with mental retardation in the study also met the criteria for autism. But he found no difference between the two age groups that would account for the recent jump in autism rates in California.
Byrd’s findings differ from those of another recent study, which found that older autistic children had been misclassified as mentally retarded at a significantly higher rate than were younger autistic children.
Byrd attributed the contradictory findings to differences in study methodology.
Overall, researchers found no demographic differences between the two age groups. Race, gender and the education of mothers and fathers were about the same in both groups. They did find, however, that more children in the younger group suffered from gastrointestinal problems than in the older group, and that fewer in the younger group also were mentally retarded.
Finally, in a finding that challenges a link between vaccines and autism, Byrd found no difference between the two groups in the percentage of children who had regressed in their development for example, by losing the ability to use certain words.
He found that about 30 percent of children in both study groups appeared to have lost developmental milestones. If a vaccine such as the often-blamed measles-mumps-rubella immunization were responsible for the autism increase, Byrd said, researchers would have seen a difference between the two groups in the proportion of parents reporting regression.
“Without that, I can confidently say (the vaccine) is not the main factor driving the numbers,” he said. “I can’t say it didn’t cause a single case.”
Byrd hopes to help conduct additional research to determine, once and for all, the possible role of vaccines in autism.
Dana Wisdom, whose 5-year-old son, Chandler, is autistic, said that in the meantime, efforts must be stepped up to help families, schools and care providers cope with the unprecedented numbers of children living with autism.
“We have a huge wave of children already diagnosed,” she said. “If we do not help these children learn and to learn how to be self-sufficient, it is going to have a huge impact on society.”