Two sources I have contacted indicate the rate of non-idiopathic autism it is indeed lower.

Sure, but they can’t really know that unless they have screened and evaluated. I’m betting they are simply wrong. In fact, 6 children with “low functioning” autism in Lancaster County is not a low count.

Two sources I have contacted indicate the rate of non-idiopathic autism it is indeed lower. These are nonscientific surveys, one very nonscientific. They also note that the vaccination rate has increased dramatically in the last 15 years, with no concurrent increase in autism.

The Amish and Mennonites (especially the “Old Order” Amish and Mennonites) have a higher-then-average incidence of genetic disorders because of a high level of inbreeding.

I don’t mean the Deliverance sort of marry-your-cousin inbreeding (although that may also occur), but the sort of inbreeding that occurs when a small population doesn’t marry outside of their group (and those that do move away from the group) and few (or no) “outsiders” join the group. This describes the Amish and Mennonites pretty well and has been going on for over a century and a half.

In any small inbred population, the genetic diversity drops over time because of the tendency to “lose” alleles for each gene through genetic drift. Eventually, this can lead to deleterious alleles (“bad mutations”) becoming more prevalent. This greatly increases the chance that two parents will each have a copy of the defective allele, which in turn greatly increases the chance of their children having two copies (and thus manifesting the genetic disorder).

But, there is a “flip” side to genetic drift in a small, inbreeding population. The prevalence of a deleterious gene can also decrease (or even go to zero), leading to lower-than-average incidence of a particular genetic disorder. Thus, it is possible that the Amish (and Mennonites) have lost some of the susceptibility alleles for autism.

Unfortunately, we have no good data on the prevalence of autism among the Amish – Mr. Olmsted’s half-hearted attempts notwithstanding. But, even if we did find that the Amish have a lower prevalence of autism, it would not necessarily have anything to do with vaccination. In fact, the most likely cause would be genetic drift and the loss of “autism alleles”.

This brings up the larger problem of studying groups that don’t vaccinate. In the case of the Amish, we’d also have to confront the fact that they are not genetically similar to the general population. By this, I don’t mean that they are “mutants” (ala “X-Men”) or that they aren’t human, just that they have a drastically different genetic diversity (and allelic distribution) than the rest of the country.

Also, if you compare the Amish to the rest of the country in respect to autism, why would you settle on vaccines as the main difference – as Mr. Olmsted implies? Why not look at their television viewing habits (very different from the general population), their exposure to plastics or their mental stress levels? Why would vaccination – arguably the practice the Amish share most with the rest of the country – be your focus?

Unless, of course, you had an agenda.

Prometheus

That’s easily the case even without considering the Amish, given that the siblings of autistic children are often unvaccinated.