Twin Study Suggests Environmental Role in Autism: Now What?
As reported last week, a large twin study supported by Autism Speaks compared the frequency with which identical and fraternal twins both share a diagnosis of autism. This approach enabled the investigators to use statistical techniques to calculate the degree to which environmental factors shared by twins contribute to their risk of developing autism. Such factors include conditions in the womb and during birth.
The results of the California Autism Twin study were game-changing because they revealed a much larger environmental influence than had previously been estimated—accounting for about 58% of the risk of developing autism. By contrast, much smaller twin studies had previously suggested that genes largely accounted for a child’s risk of autism.
The results underscore the need to investigate the role that non-inherited risk factors play in the development of autism spectrum disorders (ASD). So what’s being done to help speed this research? And what role are Autism Speaks and its donor dollars playing in this effort?
Autism Speaks has funded over $21 million in the study of environmental risk factors, an initiative we call (obviously enough) the Environmental Factors of Autism Initiative. Already, we have a large body of evidence suggesting that it is not any one environmental factor, but many different factors working together, that elevate the risk and severity of autism in individuals with a genetic predisposition for this condition. In other words, autism is seldom caused by any one thing and neither is it an “all or nothing” condition. Furthermore, different combinations of genetic and environmental risk factors contribute to individual cases of autism.
Within the Environmental Factors of Autism Initiative are ongoing studies focusing on environmental exposures that occur before and during pregnancy and throughout the first year of life—crucial periods for human brain development. These studies look at such possible risk factors as maternal and paternal age, socioeconomic status, season of birth, exposure to chemicals or toxic agents, nutrition and exposure to various pharmaceutical drugs during pregnancy, the difficulty of labor and delivery, and various other forms of prenatal stress. The researchers we support are also investigating the mechanisms by which genes and the environment may interact (so-called epigenetics) and the role of the immune system. We are also supporting large scale epidemiological studies that focus on pregnancy and the first year of life. These include the EARLI study and the IBIS study.
Are you interested in learning more about the studies Autism Speaks is funding with donor dollars? We are proud to debut the new Grant Search function on our website. Please use it to explore past and present research studies by topic or location. And if you or your family is affected by autism, please consider participating in one of our clinical studies.