The big news about autism, though, is that it seems to have become much more common during the last two decades.
The Pima County branch of the state Division of Developmental Disabilities addresses four disabilities: autism, mental retardation, cerebral palsy and epilepsy. In terms of the number of causes, autism used to be fourth. It's now third--and closing in on second.
This naturally raises questions about what could be causing so many apparently normal infant brains to go haywire after a year or two, and these are questions that young families are asking with some urgency. Nothing about autism, though, is clear or simple, and some experts even doubt that the apparent increase reflects anything more than improved diagnosis and reporting.
Researcher James Adams, professor of mechanical and chemical engineering at Arizona State University, is an expert on heavy-metal toxicity and the co-author of several studies on the biomedicine of autism. He's also the father of a 13-year-old autistic daughter, and he has strong private opinions on the subject--but he's careful to lay out the facts impartially.
"There is no doubt that the number of reported cases has dramatically increased, from three or four cases per 10,000 20 years ago to one in 166. And according to the best data we have, which is from California, where there's a fixed set of diagnostic criteria and a good reporting system, cases have increased every year that they've been counting--until last year, when there was a slight decrease," says Adams.
"That could be a statistical blip, but coming after an unbroken string of increases, it may be significant."
The numbers from California may provide an argument against increased awareness and reporting as the sole cause of the jump in autism cases: If the trend in California holds, that will seem to support the theory that increased vaccination, and specifically increased childhood inoculations with vaccines containing mercury, is at least partly responsible for the reported rise in autism and other neurological disorders (including ADD, ticking and hyperactivity) and in immune disorders in American children since 1989. The vaccination argument, which is waged with intense conviction on both sides, was made in some detail by Robert F. Kennedy Jr., in an article jointly published last June in Rolling Stone and at Slate.com.
Suspicion about vaccination as a cause of autism probably began with the stories, including that of one family interviewed for this story, of children who developed immune-system problems and regressed into autism after an immunization made them sick. (The family in question asked not to be identified, because talking about their experience in the past has provoked hate mail and angry phone calls. Anger against immunization opponents seems to run as hot in the medical community as anti-vaccination feelings do among the parents of autistic children. As one observer at a recent national scientific meeting on autism observed, "We're in a sort of frenzied period right now.")
Then there's the coincidence of the timing of a jump in childhood immunizations and the onset of what some people call the autism epidemic. Autism has increased 15-fold in the U.S. since 1991. That was the year the CDC and the Food and Drug Administration recommended that three additional vaccines, all preserved with thimerosal, a known neurotoxin, be given to young babies. (One of these vaccinations is administered within 24 hours of birth.) In addition, the overall vaccination schedule doubled during roughly the same period. American preschoolers received 11 vaccinations each before 1989; in 1999, they received a total of 22.
Of course, many other things have changed during the last 17 years, but an appearance of concealment on the part of the CDC and FDA hasn't helped reassure parents. In 2001, after reviewing an immediately embargoed 2000 study by the CDC of a possible connection between thimerosal and autism, the FDA "urged" vaccine manufacturers to stop using thimerosal in childhood vaccines, and the mercury compound has been greatly reduced in or eliminated from most vaccines since then (but not in flu vaccines given to pregnant women and young children). Existing stocks of thimerosal-laden vaccines were used in this country through 2003, however. What remained was not destroyed, according to Kennedy, but was sold off for use in the Third World, where there have been scattered reports of "outbreaks" of autism.
Many people who believe that the increase in childhood vaccinations accounts for the increase in autism argue that the drop in reported cases in California is evidence for their position: Autism typically shows itself in the second and third year of life, and so a drop last year is what you'd see several years after thimerosal was largely phased out, if it had been responsible.
California has banned thimerosal from all childhood vaccines, including the flu vaccine, beginning this July. The preservative is not necessary for vaccines that are packaged as single doses, and some vaccines, such as measles-mumps-rubella, have never contained it.
While the CDC and FDA have moved steadily to reduce thimerosal since 2001, they have just as steadily denied seeing any link between it and autism, and some observers, including Kennedy, have accused government agencies of concealing data to protect vaccine manufacturers from possible litigation and to give them time to sell off stockpiles of mercury-laced product. Rep. Dan Burton, R-Ind., who has an autistic grandson, has accused the FDA and other public-health agencies of "institutional malfeasance for self-protection" and "misplaced protectionism of the pharmaceutical industry."
Other members of Congress have reacted differently. Kennedy reports that the day after Senate Majority Leader Bill Frist, R-Tenn., a medical doctor, attached a rider known as the "Eli Lilly Protection Act" to a 2002 homeland security bill, Lilly, a major vaccine manufacturer, "contributed $10,000 to his campaign and bought 5,000 copies of his book on bioterrorism." Congress later repealed the measure, but early last year, Frist attached another provision to an anti-terrorism bill "that would deny compensation to children suffering from vaccine-related brain disorders." The prospect of thimerosal lawsuits understandably alarms the pharmaceutical industry, and Frist, according to Kennedy, has received more than $800,000 in contributions from pharmaceutical companies.
James Adams, whose daughter was severely autistic when first diagnosed but who has improved with intensive intervention, including biomedical treatments, concentrates on the research.
"The data is mixed, and more work needs to be done, but there are some small studies that suggest a connection between mercury toxicity and autism. We are also trying to determine why some children are more vulnerable than others."
Adams himself has done several studies, one of which measured the amount of mercury in the baby teeth of autistic children compared to those of normal children. He found three times as much mercury, on average, in the teeth of the autistic kids.
In another study, severely autistic children who took a medicine that pulls heavy metals out of the body--an FDA-approved treatment for lead-poisoning--excreted three to six times as much mercury as did neurologically normal children.
"We also have indications that children who are autistic have a decreased normal ability to excrete mercury," says Adams. "They're genetically more susceptible to damage from heavy-metal exposure."
And in the first-ever study of the effects of thimerosal exposure on baby animals, says Adams--incredibly, the study was done at Columbia in 2004, less than two years ago--two strains of mice were unaffected, while a third suffered profound neurological damage from exposure levels consistent with those of an infant receiving vaccine preserved with thimerosal.
"These studies, including my own, need to be replicated," says Adams. "That's what I can say as a scientist. But I have very strong private opinions about heavy-metal toxicity and autism."
Adams points out that other potential sources of mercury exposure for very young children include industrial pollution, amalgam fillings and contaminated seafood. Thimerosal may not be the only culprit.
And yet, as one parent of an autistic child says, "You know, just on the face of it, injecting babies with mercury doesn't seem like a really great idea. Where were the pediatricians?"