Autism: A Disconnect between Science and Public
March 25th, 2010 at 6:38 pm
In the last two decades or so, we have witnessed a dramatic rise in autism. According to the Centers for Disease Control and Prevention (CDC), which has been conducting numerous studies with other institutions, autism affects roughly one percent of American eight-year olds —disproportionately male — and the numbers keep going up.
The epidemic is not confined to the United States; it's worldwide. Although the recent CDC figures reflect an autism "spectrum," which includes the much milder Asperger's, the kind of autism that seems to be epidemic is the unsubtle and disabling variety with the marked indicators of unresponsiveness to others, repetitive behaviors, and intolerance for even minor changes of routine. Cognitive development is very limited; about 75 percent of autistics are mentally retarded, even though most are born to parents of normal —even very high— intelligence.
Autism presents a very distressing situation to families. These children require an enormous amount of special care and patience, the kind that leaves parents exhausted and frustrated. Few autistic children outgrow the condition. For most parents, it is all care all the time, devoid of the pleasure of their child's affection and communication. In addition to the demands autistics unwittingly make, many have chronic medical problems, such as gastro-intestinal disorders, that require frequent and expensive treatment.
Searching for the cause
Finding the cause(s) of a complex condition such as autism typically begins with a search for correlations between autism and potential causes: vaccines, genes, diet, environmental factors, toxins, and other possible culprits. But, as they say, a correlation is not the same as a cause. In the scientific method, establishing a correlation between a phenomenon and possible causal factors is only a first step in a lengthy procedure. The necessary research is tedious and it takes time. Long ago, when lab technology was quite limited, it took years to prove the link between mosquitoes and yellow fever, and years to prove the link between polluted water and cholera. In both cases —and many others—the true cause was at first dismissed, and it took a long time before the facts were accepted. In those times, bizarre theories were far more popular, not only among the public, but within the scientific community. More recently, and with more sophisticated science, it still took years to establish a link between tobacco and lung cancer, and between hormone replacement therapy and breast cancer. Again, there was great resistance to the facts.
No individual can acquire enough knowledge about all the issues we must deal with today. We all rely on experts to determine the validity of research on many subjects. Almost everyone is vulnerable to erroneous conclusions from ongoing research or to bogus claims from self-ordained "experts" whose motives are questionable. And for conditions such as autism, where there are many possible causes, there are long periods of scientific uncertainty as one possible cause after another is investigated until an answer emerges. It is understandable that the parents of autistic children are often impatient with scientific procedure.
A quick overview of the possible causes under investigation reveals just how difficult the challenge is. And one of the chief problems is the nature of scientific studies. Correlations can be found between autism and any number of factors.
Suspect #1: Vaccines
The vaccine for measles, mumps and rubella (MMR) was one of the first suspects in the mysterious increase of autism. In the 1990s some parents noticed the onset of autistic symptoms shortly after a child got the MMR vaccine. Although clearly the vast majority of children who got the vaccine did not become autistic, a link between the vaccine and autism was easily assumed. The suspected source was the trace preservative in the vaccine, thimerosal, which had been used in vaccines for many years. Although many scientists were convinced there was no link between thimerosal and autism, the preservative was removed from vaccines in 1999 as a precaution. But the autism figures continued to climb. When a study linking autism to the mercury in MMR inoculations was published in the prestigious journal, Nature, it carried the imprimatur of experts and so was accepted as fact. Later, it was revealed that the data had been falsified; the study was withdrawn with apologies from the journal.
By the time the scientific community had firmly rejected the notion of MMR as the cause of autism, however, the belief that the vaccine was somehow triggering autism was quite entrenched in the popular imagination, and many parents still refused to inoculate their children. The thimerosal theory was replaced with a belief that the vaccine was damaging children's immune systems, thereby making them vulnerable to autism. Labs around the world investigated. Carefully designed studies confirmed that there was no relationship between the MMR vaccine and autism. But it hardly mattered to the anti-inoculation movement; once again, an entrenched belief had trumped the efforts of science. As a result of the rejection the MMR immunization there were outbreaks of measles, mumps and whooping cough —along with the unrelenting increase in autism.
Suspect #2: Diet
Autistic children often have digestive problems, so the notion that dietary factors might trigger autism became quite popular in tandem with, or as alternative to, the suspicion of the MMR vaccine. Gluten and casein, found in cereal grains and dairy products respectively, were particular gastrointestinal irritants. Many parents of autistic children were convinced that special diets would eliminate both the digestive problems and autism itself. While for some there might be considerable relief, the number of actual "cures" of autism following diet modifications must have been vanishingly small. Nevertheless, to this day there are many "experts" promoting special diets as a cure for autism.
Another potential dietary culprit emerged when a large number of autism cases were discovered among Somali refugees in the United States and Europe. A link between autism in this population and a vitamin D deficiency was suggested. The hypothesis would seem to be quite a stretch, since children from very poor nations often suffer from severe vitamin, mineral and protein deficiencies. More significant, perhaps, is the fact that the autism outbreak among Somali children seemed to occur in their adopted countries. The affected children were either born after their parents arrived, or the autism emerged several years after the children immigrated. The vitamin deficiency theory seems a very weak hypothesis, even if in fact a deficiency could be found.
Suspect #3: Genetics
Another major suspect has been genetics. In an era when we invoke genes to explain almost everything, it's not surprising that the search is on for one or more autism genes. And the rate of autism among twins —90 percent— reinforces the suspicion of a genetic basis for autism. There are certainly families with a history of autism, but not nearly enough to account for the numbers we are seeing worldwide. A mutation that could be firmly linked to the autism spike would have had to develop very suddenly, and that is not the normal mutation scenario. Further, the fact that autism affects twins so consistently does not necessarily establish a case for genetic predisposition. The nearly identical makeup of twins would obviously make each pair equally susceptible, before or after birth, to toxins or other potential triggers of autism —including, the MMR vaccine if that were the cause.
Less than a generation ago, psychiatrists simply blamed autism on bad mothers. Now, in a slightly more scientific era and with more respect for mothers, we include both parents and try to determine whose genes are more responsible for autism. Some studies suggest the genetic problem is passed on by the mother, not the father. And there are studies that claim that women who give birth after the optimal age range are more likely to have autistic children. However, there are also indications that autism might be associated with older fathers. Worldwide figures are not available, but it has been noticed in the United States that many well educated parents —especially computer and engineering types—have autistic children. From such confusing data we can draw almost any conclusion.
Suspect #4: Environment
We have slowly come round to suspecting a link between autism and something in the environment. There is no question that the developing brain is highly sensitive to environmental poisons, both in the fetal stage and in early childhood. Lead and mercury are familiar in this respect, but it is important to remember that historically, it has always taken a long time, even when the toxin is clearly identified, to get federal regulations for the protection of children. Environmental toxins are endemic today, and may be affecting the human genome in ways that are completely new and unexpected.
Meanwhile, the uneven manner in which toxins are geographically distributed may cause researchers to overlook possible environmental factors and focus instead on genes and other suspected causes of autism. Consequently, when studies began to show the unusual concentration of autism in California's Silicon Valley, researchers looked for a correlation between autism and genes, autism and educated parents —specifically a kind of "geek" predisposition to autism. At the same time, the autism spike among children of Somali refugees, which in such an impoverished community could not be attributed to engineering genes, was attributed to a vitamin deficiency. It is hardly a wonder that parents of autistic children are sometimes unimpressed with the scientific approach.
One thing that all these children —and their parents have shared—is exposure to chemicals whose effects we simply do not understand yet. Phthalates, for example, are known neuro-toxins, and they are found in countless household products. Other toxins are found in the vinyl, plastics, wood and other products that are part of everyday furnishings. For a while, these chemicals seemed to be disregarded, but researchers are beginning to look more closely at the many ordinary substances in our lives. When we consider these substances in conjunction with food additives, pesticides, herbicides, hormones in our environment, we might realize that there is a very real possibility of a connection between this unprecedented chemistry and a whole range of neural disorders.
The need for comprehensive research
Oddly, the research so far seems to focus on very limited geographical or environmental situations. A great deal of attention is directed to the California autism spike, even though the problem is worldwide. There is a focus on this or that chemical or dietary factor in a limited population or community, although the same factors are widespread. We have reached a point of distraction with motley correlations. The public needs multinational studies which compare a larger range of factors, and such studies should include environmental and toxicological data. A comprehensive approach is the only way to ensure that way the public can obtain the best information.
Autism might be caused by more than one thing, and what triggers it in one child may differ from what causes it in another. It will probably take time to identify the source(s) of the problem. But the scientific community has a serious dual responsibility here: first, the responsibility of explaining the challenge of the research effort itself; and second, the responsibility of devising more comprehensive studies that include realistic potential causes of autism.
Yvonne Stapp March 25th, 2010
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