Autism Round Up

I've accumulated a few articles on autism that I think need some air.  Autism is serious problem for many families, and because it is so poorly understood, it generates a lot of guilt, angst and blame seeking by parents of affected children:

Non-genetic factors play surprisingly large role in determining autism

A new Stanford University School of Medicine study of twins suggests that non-genetic factors play an unexpectedly large role in determining autism risk, turning upside down recent assumptions about the cause of this common, disabling developmental disorder.

From prior studies of shared autism in twins, scientists had estimated that 90 percent of autism risk was attributable to genes and only 10 percent to non-genetic environmental factors. But the new study — the largest ever of twins in which at least one in each pair has autism — shows almost the opposite: It found that genes account for 38 percent of autism risk, with environmental factors explaining the remaining 62 percent.

However, skeptics of the study spoke up almost immediately, accusing the new group of representing advocacy groups, and misinterpreting their own results:

Autism experts skeptical of study linking disorder to environment

The LA Times points out that their calculations are subject to a wide margin of error and could be wrong, but the conclusions point to more research into environmental factors that may contribute to autism, including environmental toxins and chemicals--not coincidentally also factors that Autism Speaks had already concluded contribute to autism's cause before the recent study was performed.

"I think they're really on shaky ground to say that," Dr. Paul Law, director of the Interactive Autism Network at the Kennedy Krieger Institute in Baltimore, told the Times.

"Their data is so similar to everybody else's, and yet they come up with another conclusion," added Robert Plomin, a behavioral geneticist at King's College London. "I don't know how this happened."

The degree of heritability of autism is one of the key questions of interest to parent seeking to assign blame.  A high degree of heritability puts the blame squarely on the parents. While they may have no control over their own genes, having them at fault leaves nothing left to blame.  On the other hand, a high degree of environmental control leaves ample room for any number of theories that could place the blame beyond the reach of the parents (like the discredited vaccine theory).

At it heart, this debate seems to be about the means and statistics of twin studies, a long used technique for determining the degree of heritability of traits.  This dispute should be readily soluble by having independent experts in statistics and genetics look at the raw data for the study.  This may be another case where peer review has failed.

Another article purports to have found a change in common in the brain at the molecular level among autism victims:

...a UCLA study is the first to reveal how the disorder makes its mark at the molecular level, resulting in an autistic brain that differs dramatically in structure from a healthy one. Published May 25 in the advance online edition of Nature, the findings provide new insight into how genes and proteins go awry in autism to alter the mind.

The discovery also identifies a new line of attack for researchers, who currently face a vast array of potential fronts for tackling the neurological disease and identifying its diverse causes. ...

"In a healthy brain, hundreds of genes behave differently from region to region, and the frontal and temporal lobes are easy to tell apart," Geschwind said. "We didn't see this in the autistic brain. Instead, the frontal lobe closely resembles the temporal lobe. Most of the features that normally distinguish the two regions had disappeared."

Two other clear-cut patterns emerged when the scientists compared the autistic and healthy brains. First, the autistic brain showed a drop in the levels of genes responsible for neuron function and communication. Second, the autistic brain displayed a jump in the levels of genes involved in immune function and inflammatory response.

"Several of the genes that cropped up in these shared patterns were previously linked to autism," said Geschwind. "By demonstrating that this pathology is passed from the genes to the RNA to the cellular proteins, we provide evidence that the common molecular changes in neuron function and communication are a cause, not an effect, of the disease."

I'm not sure I understand the ramifications of this one.  Are they proposing a chemical test for autism?  I don't see how this bears on the heritability of autism; the expression of genes could be a cause, but they could also be an affect of whatever process leads to autism.

Finally, one that I consider to be true crap:

Autism May Have Had Advantages in Humans' Hunter-Gatherer Past, Researcher Believes

The autism spectrum may represent not disease, but an ancient way of life for a minority of ancestral humans, said Jared Reser, a brain science researcher and doctoral candidate in the USC Psychology Department.

Some of the genes that contribute to autism may have been selected and maintained because they created beneficial behaviors in a solitary environment, amounting to an autism advantage, Reser said.

The "autism advantage," a relatively new perspective, contends that sometimes autism has compensating benefits, including increased abilities for spatial intelligence, concentration and memory. Although individuals with autism have trouble with social cognition, their other cognitive abilities are sometimes largely intact.

The paper looks at how autism's strengths may have played a role in evolution. Individuals on the autism spectrum would have had the mental tools to be self-sufficient foragers in environments marked by diminished social contact, Reser said.

The penchant for obsessive, repetitive activities would have been focused by hunger and thirst towards the learning and refinement of hunting and gathering skills.

I would rather imagine that autism is the result of imperfections and variations left over from the relatively rapid evolution of the human brain, over the past sever hundred thousand years.  Much like the appendix, and wisdom teeth which continue to plague mankind, it takes millions of years for evolution to craft a finely honed organ, and the human brain has simply evolved too rapidly to have achieved any level of perfection.  Therefore a fair number of random deficiencies make themselves apparent in the course of development.  After a few more million years of selective evolution, with autistic individuals having dramatically reduced opportunities to reproduce, I imagine the autism strikingly reduced, if not altogether eliminated.