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By The World Mercury Project Team

Genetics is the darling of the biomedical research industry. For diseases ranging from cancer to skin disorders, investigators have been busily at work for decades trying to identify the conditions’ underlying genetic causes. However, these same investigators—and the reporters who communicate their findings to the public—are often strangely incurious about the role of environmental toxins as triggers of disease.

A story about autism spectrum disorder (ASD) published in October 2017 by the news website Vox furnishes an example of this genetics-as-the-explanation-for-everything perspective. Vox senior health correspondent Julia Belluz (a self-described “evidence enthusiast”) interviewed a small sample of five reportedly “cutting-edge” autism researchers, all of whom focus on autism genetics. Given the lack of disciplinary diversity in her selective sample, Belluz’s conclusion that genetic factors are the most “well-established” and “promising” explanation for autism comes as no surprise.

Two of Belluz’s five interlocutors (geneticist Stephan Sanders and psychiatrist Lauren Weiss) are researchers at the University of California-San Francisco (UCSF), but neither one mentions a rigorous population-based study of 192 twin pairs published in the Archives of General Psychiatry by UCSF researcher Neil Risch and colleagues in 2011. Risch is the director of UCSF’s Institute for Human Genetics. The study’s results indicated that “environmental factors have been underestimated, and genetics overestimated, for their roles in autism-spectrum disorders.” Another study that involved families with two ASD-affected siblings (published in Nature Medicine in 2015) likewise highlighted “substantial genetic heterogeneity” in ASD, again suggesting that environmental or other shared risk factors trump heritability.

…environmental factors have been underestimated, and genetics overestimated, for their roles in autism-spectrum disorders.

To be fair, Belluz’s discussion gives a nod to a “genes plus environment” perspective on autism causation by acknowledging that an “underlying genetic predisposition or mutation” generally needs to “collide” with environmental triggers in order to give rise to ASD. However, Belluz characterizes the research on environmental risk factors for ASD as “blurry,” “murky,” “mixed” and not “robust.” Belluz also cites a study that, according to her, views shared genetic variants in families as “probably more important” as an autism trigger than shared environments. However, the article actually emphasizes gene-environment interactions and concludes that “the amount of evidence supporting a significant contribution of environmental factors to autism risk” makes it clear that “the search for environmental factors should be reinforced.”

A pivotal paper published in early 2017 goes a step further, asserting that “The term ‘heritability,’ as it is used today in human behavioral genetics, is one of the most misleading in the history of science.” The paper’s two authors argue against the “deeply flawed” assumption that “genetic influences…can be separated from their environmental context.” According to these authors, “contemporary biology has demonstrated beyond any doubt that traits are produced by interactions between genetic and nongenetic factors that occur in each moment of developmental time. That is to say, there are simply no such things as gene-only influences [emphasis in original].” Stated another way, the paper suggests that “it makes little sense to attempt to quantify the relative importance of two different factors that interact with one another [dynamically] to produce an outcome.”

Read the full article at World Mercury Project here.