Five researchers in Italy have proposed a comprehensive hypothesis for the etiology of the autism epidemic.
First, I want to tell readers why I think the incidence of autism is actually increasing and that the increased incidence is not just due to better recognition. Autism is not a subtle disease; it is not easily missed. The children usually do not speak or have impaired verbal communication. They rarely have a single friend. They frequently perform repetitive behaviors, and they often fly into rages over a little change in their routine. There is nothing subtle about autism.
The geneticists, who correctly know that autism is highly heritable, realize that a genetic disease cannot explode in incidence, especially as autistic individuals seldom reproduce. The autism genes cannot suddenly become more common in the gene pool, so the geneticists have to say that the disease was simply not recognized in earlier times. Otherwise they have no explanation for a genetic disease becoming epidemic in one generation. But what are the implications of the better recognition hypothesis?
It means that the teachers, parents and the doctors of the 1950s, 60s and 70s simply overlooked these autistic children. They did not recognize the disorder, while parents, teachers and doctors are recognizing it today. Again, that would have been impossible as autism is a non-subtle and obvious condition. Another way of saying it is that the better recognition theory has no face validity. In fact, when you think about it, the better recognition theory is ludicrous.
However, I do believe that some of the increased incidence is due to diagnostic substitution, meaning that autism diagnosis was substituted for another condition. It is true that as the diagnosis of mental retardation decreased, the diagnosis of autism increased. However, I think this only explains a small fraction of the increase incidence of autism. It is clear that this highly heritable condition is exploding in incidence. How can that be?
In this recent paper, the five Italian researchers put all the latest evidence together into one comprehensive theory. They agree that there is a strong genetic contribution and those genes interact with the environment. As others have done, they view autism as a disorder of the immune system that occurs in a very early phase of embryonic development. In other words, they view it as an autoimmune disorder, like rheumatoid arthritis, but the body’s deranged immune system is attacking the brain instead of the joints. They see a background of strong genetic predisposition interacting with vitamin D deficiency which dysregulates the immune system. Then a viral infection or another insult triggers a deranged immune response which, in turn, causes autoimmune damage to specific areas of the brain during gestation.
I agree with everything except when the insult occurs. There is a very interesting study showing that the onset of autistic symptoms occurs between the ages of one and three.
I have noticed a similar thing in our enrollees in our autism clinic. The majority of parents report normal developmental milestones in early infancy with either lack of additional progress or deterioration between the ages of one to three.
So, it is possible that some sort of insult occurs during pregnancy in some, and during toddlerhood in others. I think that in most autistic children, the deranged immune system does not deal with the insult until toddlerhood, when young children have no apparent source of vitamin D.
When I say no apparent source of vitamin D, I say that because most toddlers are no longer weaned on vitamin D enriched cow’s milk, most do not take vitamin D supplements, and most parents make sure toddlers avoid the sun or wear heavy sunblock. Where do toddlers get their vitamin D?
They don’t, which I believe injures their immune system, triggering the autoimmune disorder we know as autism.