A SECOND OPINION http://atlanta.creativeloafing.com/gyrobase/Content?oid=96072

Regarding your Fallout piece titled "Moms push mercury-autism link" (July 6), the evidence against a causal link between vaccinations (thimerosal containing MMR vaccines in particular) and autism is incontrovertible. Several large retrospective epidemiological studies have shown that when autistic children's immunization records are compared to normal children's, they have equal rates of having been vaccinated. One would expect at least a slightly higher exposure rate in the autistic sample if vaccines caused autism.

Additionally, looking at twin studies in which one sibling is affected with autism, when you compare identical twin sets (having identical genes) with fraternal twin sets (sharing a minority of genes) the rates of autism drop from 92 percent to 10 percent. At the Emory University Autism Center, and other such facilities, there is now a battery of genetic tests that affected children are given to elucidate possible causes in individual cases. The list of known genetic variants leading to autism has grown and has highlighted that the disorder is characterized by a spectrum of different developmental anomalies in the brain and nervous system.

So if autism spectrum disorders are genetically determined, as the above studies would suggest, why is there a dramatic increase in affected children? The answer is that the disorder has become better recognized and diagnosed. As rates of autism have increased, rates of various forms of mental retardation and learning disabilities have decreased proportionally. In other words, a kid that in the past would have been labeled mentally retarded and perhaps even institutionalized, is now properly diagnosed and offered effective treatments early on to limit the social and behavior manifestations of the disorder.

I can sympathize with the frustration of parents dealing with children affected by this condition. The need to blame people, corporations or organizations such as the CDC is understandable. But groups like Moms Against Mercury, sadly, are not going to save future children from developing autism. Instead, they are likely to drive parents away from providing life-saving vaccinations for kids, perhaps leading to future epidemics of measles, mumps, rubella and other infectious diseases that have been largely eradicated in this country since immunization programs began.

I would encourage young parents considering the risks of vaccinating their children to talk with their pediatricians and educate themselves about this question. Hysteria about corporate greed and government cover-ups will not benefit children.

-- Clifford J. Ehmke, M.D., Atlanta

Emory University Department of Psychiatry