Medscape: Where do the data stand on potential environmental influences in autism and ASDs?
Dr. Volkmar: The interesting thing about environmental studies is that they've been much less productive than we expected. However, there a number of interesting studies here. For example, there were a group of children who grew up in the horribly depriving orphanages in Romania, when Romania was a communist country. These were just dreadful institutions and the children looked very autistic. The interesting thing is they were followed over time as researchers thought, "Oh, we might have an environmental model of autism related to severe deprivation." As those children were placed in more supportive family environments, they got better. I'm not saying they became perfectly normal, but it was a very different kind of course.
There was an eminent child psychiatrist named Stella Chess who wrote about children with congenital rubella, a congenital infection that often leaves babies blind and deaf. She wrote about them having what looks like possible autism. The interesting thing again with those children is that over time they looked less so, and of course children with very severe problems like blindness and deafness associated with congenital rubella are difficult to assess. And so we've learned to be a little careful about this because it's a slippery slope. Sadly, it's a little like the joke about asking Mrs. Lincoln how the play was. Because there's so much else going on, this is just not adding very much. And the trouble is that the issues of diagnoses are actually, especially in classical autism, most complicated at the bottom and top of the IQ range. The middle range is less complicated.
In the very impaired child with mental retardation, what's now called intellectual deficiency, there are many autistic-like behaviors, such as motor mannerisms and unusual movements. Often those children don't have social difficulties that are more profound than their intellectual disability. That's one of the great complexities with dealing with all this.
And, of course, there was a lot of interest in the last few years about that work suggesting that perhaps the measles-mumps-rubella vaccination had some role in autism. That paper has been withdrawn, as I understand it, from The Lancet. It is surprising that more hasn't panned out about the environmental causes.
One area that has some potential relevance is whether very premature infants are more likely to have autism or ASDs. There is a small body of work on this but it is growing. In some ways it is interesting in that it may parallel some of the older work on animal models of autism using lesion studies. That is, there may be some potential for linking damage in some areas of the brain to behaviors and developmental features similar to those seen in autism. On balance, however, while there has been some research on environmental factors in autism, there is much less evidence here as compared with genetics.
Medscape: Do most experts believe there probably is, at least in some cases, an environmental component to autism?
Dr. Volkmar: Well, there's certainly some potential here. Even if you look among identical twins, the concordance for autism is not perfect, although it is very high. But again even here, keep in mind that identical twins in utero may be exposed to different things. So there is certainly a potential role for environmental factors, but the data for now are lacking.
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Cite this: Two Major Concerns in Autism - Medscape - Jul 10, 2012.