An article was recently published in the General Archives of Psychiatry concerning the relative contribution of environmental influences vs. genetics in causing autism. Comprehensive analysis of twins suggests that environmental factors may be at least as important as genes in causing autism.
The study looked at twin pairs born between 1987 and 2004 with at least one twin having an autism spectrum disorder. Unlike previous studies, this one included structured clinical assessments and direct child observations to establish a diagnosis of autism or autism spectrum disorder. In all, 202 twin pairs participated in the study.
The results are quite interesting and unexpected. Previous studies found a significant contribution of genetic factors to the development of this disorder. However, this study found something different. Approximately 38% of the risk of having autism is due to genetic factors with the rest, around 62%, due to shared environmental factors, suggesting that the conditions that twins shared in the womb are highly significant in the development of autism.
The idea that environment is so influential in causing autism is quite surprising, particularly to an autism psychologist such as myself who sees autistic children from families where there is hardly any evidence, at least on the surface, of exposure to environmental factors that might cause autism. And because autism is evident very early in a child’s life, the environment seems an unlikely contributor. How is it possible that something in the child’s external world causes autism?
The answer, unfortunately, is not addressed in the article. No specific environmental factors are listed, so we are left with a statistical result, gained from studies of twins, which is quite compelling but without the most important piece of information: the exact cause of this disorder.
What the article does say is that environmental influences might involve prenatal factors, not just those occurring to the child after birth. It is possible that diet or medications taken during pregnancy could lead to autism.
What does all of this mean? For one thing, prenatal care is critical. A pregnant mother should pay careful attention to her heath, including which foods she is eating and what medications she is taking, and she should consult closely and frequently with her physician. We have evidence that genes alone do not cause autism, but also what happens during pregnancy and immediately after birth.
As an autism psychologist, I am committed to seeking out studies that help us understand the causes of autism spectrum disorder and sharing my findings with people who are affected by autism. I welcome all comments about this topic and hope to generate a discussion that will benefit all of us who wish to understand and help those with autism.