A recent two studies suggest that environmental aspects may play a bigger role in autism than was believed formerly. The first study by a team Stanford University inlvoved fifty-four pairs of matching twins, who share one hundred percent the same genes and one hundred and forty pairs of fraternal twins, who share half of the same genes.
The team compared cases of autism in identical and fraternal twins and revealed that fraternal twins usually have higher rate of autism, which suggest that aspects other than genetics may be triggering the condition. In each pair about one of the twins had been diagnosed with autism.
The second study by researchers from health insurer Kaiser Permanente revealed that mothers of autistic children were prone to have been prescribed a common antidepressant by twice during the year prior to their pregnancy than mothers of healthy children. The risk was even higher, when the drug was taken in the first trimester of pregnancy.
The odds of both children suffering autism spectrum disorder were higher among identical twins than among fraternal twins. But fraternal twins were much more likely to develop autism than studies of children in families where a sibling has autism, revealed researchers.
Autism is a spectrum of disorders varying from a deep incapacity to communicate and mental retardation to comparatively mild symptoms such as with Asperger’s syndrome. It can affect one in every one hundred and fifty children born or about one percent of population.
According to study author Dr. Joachim Hallmayer of Stanford University School of Medicine in California, environmental factors play a bigger role than previously thought. Environmental aspects common to twins explain about fifty-five percent of the cases of autism, while genetic aspects still play a role. It is much lower than seen in other studies of twins and autism.
The findings, published in the Archives of General Psychiatry, suggest that something in the birth environment such as drugs, chemicals or infections may be triggering autism in children those who are already genetically predisposed to develop the disease. It has already been known that genetic aspects add to risk of autism.
They now have strong evidence that, on top of genetic heritability, a shared prenatal environment may have a greater than previously realized role in the development of autism, explained Clara Lajonchere, study co-author and vice president of clinical programs for Autism Speaks.