Autism May Be Caused by Environmental Factors, a Study Says
A study of identical twins at Stamford University and University of California- San Francisco (UCSF) showed the possibility of autism to be caused by environmental factors. This finding is likely to swing in the emphasis of research into developmental disorder. These factors, which include conditions in the womb, could be at least as significant as genes in causing autism, the study says.
The study examined 54 pairs of identical twins and 138 fraternal twins in California where at least one twin had autism using a mathematical model. The researchers found that 38 percent of the risk of autism is accounted by genetics while environmental factors account for about 62 percent. According to the study, the rates of autism in fraternal twins were higher than anticipated, 36% for females and 31% for males. In this scenario, the common factor is the maternal womb, emphasizing the likelihood of pregnancy as a major period in development where external factors such infections, chemical exposure and maternal stress might exert an influence.
Dr. Peter Szatmari, an autism researcher and McMaster University child psychiatry and behavioral science head, mentioned the importance of the study to confirm the involvement of genetic factors in the cause of the disorder. However, he added that the study shifts the emphasis to the potential that environmental factors could be significant as well.
Previous studies on twins had indicated the inheritability of autism, with genetics accounting for 90 percent of all cases in the world. Because of this, current studies on autism have focused on tracking down the genes and revealing the complex genetic codes that have to do with autism.
Nil Risch, UCSF Institute for Human Genetics director and the developer of the study, noted that they are not pointing out that there is no genetic component involved in autism; however, for many people with autism spectrum disorder, it is not only genetic that is involved.
Usually, twin studies are used to distinguish between genetic and environmental influences on medical disorders. Almost 100 percent of the genes are shared by identical twins and fraternal twins share half of their genes. In these cases, the early development of the siblings, both in the womb and after birth, are expected to be very similar. The emphasis on genetics as the primary cause of autism has been placed by various studies in the past decade.
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