Does watching TV influence autism?

Even if it's not true, perhaps it will scare people enough into actually spending time with their kids instead of setting them in front of the electric babysitter.

All Things Considered, March 15, 2007 · A new study links autism to subtle changes in a wide range of genes. The finding, published in the journal Science, suggests that autism has many causes, and that whatever triggers autism usually occurs long before birth.

The study, led by Jonathan Sebat, a geneticist at Cold Spring Harbor Laboratory in New York, examined the genes of 264 families. Some families had members with autism, others did not.

Sebat says the goal was to compare the genes of autistic children with the genes of their parents.

"By comparing the two," he says, "we could find a mutation in the child that was not inherited from either parent."

It turned out that children with autism were much more likely than other kids to have these "spontaneous" mutations. The mutations affected bits of genetic code that tend to appear more than once, like duplicate copies of certain pages of a book.

In many children with autism, some of the duplicates were deleted.

For example, Sebat says one child in the study was missing a copy of the gene for oxytocin - a hormone that seems to influence social behavior.

"That child has one copy of oxytocin instead of the normal two copies," Sebat says, "and that may have resulted in the corresponding decrease in the levels of oxytocin."

It's a change that could have affected normal social development.

But Sebat says that in other children with autism, the deletions affected other genes.

"There may in fact be many genes ?- I would speculate 100 or more ?- that play some role in cognitive development, and when they are altered, could cause autism," Sebat says.

That's many more than researchers have found involved in inherited autism.

Sebat's research is causing a lot of excitement among autism researchers, including Ezra Susser, an epidemiologist at the Mailman School of Public Health at Columbia University and the New York State Psychiatric Institute.

"It changes our thinking about what kind of genetic causes are important," he says, "and knowing that changes our thinking about what kinds of environmental causes are important. Because I think everybody believes that there is an interplay of genes and environment in most diseases, and that would be true for autism, too."

The sort of mutations found in the study tend to occur in eggs or sperm before conception or in the earliest stages of an embryo's development, Susser says.

The finding suggests that things such as exposure to vaccines after birth probably aren't the main causes of autism.

Susser also says the study suggests a new direction for researchers seeking the causes of autism.

"It doesn't mean that we should stop looking for [early-life] exposures," he says. "It does not mean that we should stop looking for early life exposures. But it does mean we should start looking for exposures that might be preconceptional also."

Susser has already shown that older fathers are more likely to have genetic mutations in their sperm, and more likely to have a child who is autistic. He says scientists need to ask whether a parent's exposure to certain chemicals has a similar effect.

In the meantime, Sebat says, the new research offers at least one practical application. Parents who already have a child with autism could undergo genetic tests to see what sort of mutations are present. If the mutations are spontaneous, rather than inherited, future children would have no special risk for autism.

NPR reported yesterday? that they've found that non-inherited autism is associated with multiple genetic mutations.

Aetiology

The causes of autism spectrum disorders are not clearly understood. It is likely to be a heterogenous condition with different causal factors operating in different groups of cases. In very few children the clinical syndrome of autism is associated with chromosomal or single gene disorders: fragile X, phenylketonurea, tuberose sclerosis, or neurofibromatosis; in others with infections, for example, congenital rubella; and in others with evidence of diffuse brain dysfunction (believed to be due to a physical or chemical fault affecting the developing brain). It is now well established that it is not related to parental personality or child-rearing practices. http://www.nevdgp.org.au/info/std_misc/Autism_hcs.htm

In the spring of 2005, Cornell University economist Michael Waldman noticed a strange correlation in Washington, Oregon and California. The more it rained or snowed, the more likely children were to be diagnosed with autism.

The more it rained or snowed, the more likely children were to be diagnosed with autism.

Current thinking relates some vaccinations (or possibly he mercury preservatives in vaccines) to autism.

18: Childhood Vaccines' Link To Autism Is Debunked
by Apoorva Mandavalli

The controversial theory that childhood vaccines cause autism was discredited by one report after another this year. The biggest blow came with the public retraction of a 1998 paper in the British medical journal The Lancet that had suggested a link between the measles-mumps-rubella vaccine and autism in a study of 12 children. Despite questions at the time concerning its scientific credibility, the report garnered a blizzard of press coverage and led some parents to put off vaccinating their young children.

In February Richard Horton, editor of The Lancet, said that the work was "flawed" and should never have been published. More reports followed. In May an expert panel at the Washington-based Institute of Medicine announced that neither the measles-mumps-rubella vaccine nor the mercury-based vaccine preservative thimerosal is associated with autism. The panel based its finding on expert testimony, published papers, and ongoing and completed research?-including epidemiological studies in the United States, the United Kingdom, and Sweden. Then in September a long-term study of more than 5,000 children in the United Kingdom?-published in The Lancet?-also found no association between measles-mumps-rubella shots and autism.

The new evidence has yet to quell the fears of some parents. In particular, uncertainty over the effects of exposure to mercury have made thimerosal a continued focus of controversy.

Arguing that the slightest risk warrants completely eliminating the preservative, the Food and Drug Administration recommended removing it from childhood vaccines. Today, except for the flu vaccine manufactured by Aventis, most vaccines contain only trace amounts of thimerosal or none.

Experts say it's crucial to win back parents who mistrust the government and refuse to have their kids vaccinated. "But there is no way we can assure them that every vaccine is safe for every child," says Christopher Wilson, chair of immunology at the University of Washington in Seattle. "That's not the case and never will be."