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Until now, the genes that you had inherited were the single most important factor to decide whether you’d develop autism. But now, a new study done on twins, has found that environmental factors also have an important say in the development of autism.

Environmental Factors have an Important Say in the Development of Autism

For long, scientists have wondered the reason behind autism. It wasn’t that long ago that mothers were held responsible for the condition in their child. They were accused of not showering enough love on the child. The neglected child, they said, developed features of the disease. Thankfully, this idea was debunked soon enough.

Later, factors like one’s genetic makeup, parental age, multiple pregnancies, low birth weight and exposure to medications or maternal infection during pregnancy were associated with the condition. Prior researches showed that almost 90% of the cases of autism were because of the inherited genes. But, this did not explain the rapidly increasing number of children suffering from autism. Our genes do not evolve so fast, scientists said. Now, a new study, which involved the largest number of twins, in which at least one in each pair suffered from autism, has confirmed the role of genes in the disease. But, in what can be termed as a major breakthrough, it has been found that it is the environmental factors that play a very important role in the condition- almost 62% cases were because of these factors as compared to just 38% cases because of the genes.

It is the Interplay between the Environmental Factors and the Genetic Factors that Leads to Autism

According to Joachim Hallmayer, the lead author of the study, which was published in the July 4 issue of Archives of General Psychiatry, the findings have surprised many. It shows that the role of environmental factors was grossly underestimated over the years. He feels that it is the interplay between the environmental and the genetic factors that leads to autism.

The study was conducted on 192 pairs of twins who received services for developmental disabilities, from the diverse population of California. It included 54 pairs of identical twins and 138 pairs of fraternal twins, wherein at least one child from each pair suffered from autism. They underwent standardized diagnostic tests to confirm the diagnosis. The rate of autism was compared between the identical twins, who share all their genes, and fraternal twins, who share 50% of their genes. Each pair shared their environment from conception to childhood. The scientists employed a mathematical model to calculate the precise genetic and environmental contributions to the risk of developing the disease. The environmental contribution to the condition was found to be much more than expected. Moreover, factors like the ages of the twins' parents, years of parental education, ethnicity, difference in birth weight between twins and gestational age at birth were not found to have any impact whatsoever in the development of autism.

What remains to be investigated is the type of environmental factors that could affect autism. Since the condition is apparent even in very small children, there are strong possibilities that these environmental factors exert themselves during pregnancy itself. According to Lisa Croen, a co-author on the study, the events that happen during pregnancy need to be explored in depth, to find the environmental factors that lead to autism.

  • “Non-genetic factors play surprisingly large role in determining autism, says study by group”, by Erin Digitale, Stanford School of Medicine, published on July 4, 2011, accessed on July 21, 2011.
  • “New Study Implicates Environmental Factors in Autism”, by Laurie Tarkan, Reuters, published on July 4, 2011, accessed on July 21, 2011.
  • Photo courtesy of mattbeckwith on Flickr:

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