Autism: Probably not caused by vaccines, mercury, television, or unaffectionate mothers.

Via Nobel Intent, a group of autism researchers has developed a genetic model of autism that comes pretty close to predicting the incidence rates that we actually observe in reality. Many researchers have aspired to this and failed, using single-mode genetic models, but this new study finds that introducing a few very specific assumptions about the genetic character of autism helps:

1. Familial susceptibility to autism is a dominant trait, with offspring of autistic parents having a 50% chance of inheriting it. (Autism is known to be passed on from observably autistic parents.)

2. But, while almost all males who inherit the susceptibility for autism develop the disorder, only about 30% of females with this inheritance do. (Boys are much, much more likely to be autistic than girls, autistic parents or not.)

3. Mutations associated with susceptibility to autism are common in the general population. (Females are very likely to act as 'non-symptomatic' carriers, so when autistic children appear in families with no previous signs of autism, they will often be in sudden clusters (rather than being interspersed randomly). Older parents are more likely to have an autistic child, as older germ cells = higher mutation rate.)

Very interesting stuff, and beats the heck out of the timeworn but still common belief that autism is caused by childhood vaccines. For other hypothesized causes, see post title.

Scientific American: Don't f*ck with the scientific consensus, man.

On Friday a SCIAM blog discussed the latest lawsuit by parents of autistic children, who claim this time that childhood MMR (measles, mumps and rubella) vaccines are to blame. The post notes that the Institute of Medicine has found no evidence for a connection between autism and MMR and other vaccines containing thimerosal (which in turn contains mercury). The parents, of course, think that these study results showing no link are 'preordained by the federal government.' The post author responds:

[I]t's not entirely unreasonable to suspect the government of mischief or playing buddy to the pharmaceutical companies. But, this is a scientific consensus--one from a respected body, to boot.

Well, then. If it's a respected scientific body we're talking about, we'd best just cease all critical thinking immediately and place our faith in their perfect wisdom. Because it's not as though respected scientific consensus on heavily charged issues has ever turned out to be incorrect before, you know? That said, the post does refer to one important fact, which is that while use of thimerosal in childhood vaccines has been virtually eliminated over the past six years, autism has continued to increase.

Nobody knows what causes autism, which is understandably frustrating for parents of autistic kids. Alleged causes range from genes to environmental pollutants to viruses. Interestingly, the Center for the Study of Autism mentions vaccines as a possible cause, but in the context of viral exposure, not thimerosal/mercury. In other words, since exposure to certain viruses actually has been linked to the development of autism, the concern is that the live or dead viruses used in childhood vaccines might be causing it as well. The Center website doesn't mention thimerosal at all, so one might wonder if focusing on that compound (which, as respected scientific consensus tells us, doesn't cause autism) shifts scrutiny away from the real concern. Which would be a big concern, if valid: if autism really is linked to viral childhood vaccines, we'd have to rethink our entire strategy of extensive vaccination of school-age children, which has been very successful in eliminating 19th century diseases like measles and smallpox.