Autism and pesticides: a misuse of scientific rigour

Autisme et pesticides – Aut’Créatifs, 9 septembre 2019.
English Translation by Emily Gray.

Autism and pesticides: a misuse of scientific rigour

On September 9, 2019, Autisme Montreal, the David Suzuki Foundation and l’Alliance pour l’interdiction des pesticides systématiques published what they referred to as a “literature review” with the title, “Alarming increase in the prevalence of autism: Should we worry about pesticides?” This report states that pesticides have an impact on the prevalence of autism.

Very disappointed, deeply concerned

We are strongly disappointed that the David Suzuki Foundation is associated with ideas that risk tarnishing its credibility. Because since its publication, this report is under criticism of eminent scientists, such as M. Sébastien Sauvé, professor of environmental chemistry at University of Montreal, and Dr. Éric Fombonne, internationally renowned child psychiatrist and epidemiologist to whom we owe the redaction of the research associating autism with the MMR vaccine in the prestigious scientific journal the Lancet.

A serious study, this time issuing from a veritable and renowned chair of university research and appearing in Jama psychiatry (psychiatry’s most prestigious journal,) just recently demonstrated that the rise in the number of autism diagnoses is connected for the most part  to the fact that the diagnostic criteria are being interpreted more and more liberally and lightly. In other words, the autism diagnosis was given to a growing number of people who are less and less different that the non-autistic population. That has evidently absolutely nothing to do with pesticides!

Autism Montreal’s usual catchphrase

Autism Montreal having apparently furnished the studies underlying this publication, it should not be surprising that all of this is, “as though by chance,” in favour of the idées-fixes (rigid opinions) that AM has been spreading for a number of years about autism. These  idées-fixes can be summarized here: Nobody is born autistic; A person becomes autistic by being poisoned by “toxins” (vague term comprising sugar, corn, colouring, yeast, pesticides, and even more); These said toxins cause “oxydative stress” and “mitrochondrial problems” resulting in autism.

These are what we politely call “alternative facts”, that not only deny a genetic basis to autism, but that have also never been validated by the scientific community. Note that by the way, fixations and “special interests”  are really not exclusive to autistic people!

From the beginning, the joint report three organisms was biased in favour of “controversial” theories another “polite” term, of Autism Montreal, whose pseudoscientific jargon is found in its pages. In this regard, it must be known that Autism Montreal is not at all a research chair in autism, but essentially a group of parents offering various services to autistic people and their families.

Major methodological gaps

Let’s go a bit deeper. The joint report talks about a “literature review.” However, by reading the methodology, it’s clearly specified that this analysis is not a meta-analysis and isn’t exhaustive of the scientific literature on the subject. It is also stated that the research tool used was Google Scholar. Therefore, multiple studies on the subject may have been omitted given the poor methodology.

The report affirms that pesticides cause autism. However, in the methodology, it’s written: “exploring if the correlations imply equally a causation.” Therefore, contrary to their conclusion, the authors affirm that they have no proof whatsoever that pesticides cause autism. The studies show only a correlation between autism and pesticides, that is to say, in our society, there is an increase in both pesticide use and autism prevalence. However, making these correlations between two variables is very simplistic. For example, a linear correlation exists between a fall in the number of divorces and a fall in margarine consumption, between Miss America’s age and the number of murders, or between the risk of death by falling down stairs and the purchase of an iPhone. In other words, almost anything can be connected to anything else. The use of a simple correlation to show a causality link is a major error in statistics and also in methodological, scientific, and ethical rigour.

The report claims that it was based on 158 studies. However, according to annex 3, they actually only used 6 different studies, and these studies in no way assert that there is a causal link between pesticides and autism. Its authors only observed that the two variables are rising throughout time. As mentioned, this is in no way proof of a cause-and-effect link. Added to this is the fact that some data is not independent and that evaluations for diagnoses are not always based on recognized protocols. Finally, this research used no control group, which is nevertheless an essential criterion in scientific research to be able to prove a cause-and-effect relationship.

In short, the fundamentals upon which this report is based are weak, questionable, and biased.


The fact remains that pesticides are indeed dangerous substances. They are poisonous to plants, animals, even for farm workers and the environment in general. This industry is far from being known for its good sense of ethics?. In Quebec, whistle-blower agronomist Louis Robert revealed in 2018 that agronomists, including state-employed agronomists, were receiving industry bonuses to incite farmers to buy large amounts of their products, including atrazine, a pesticide banned in Europe since 2004 due to its high toxicity. Some members of Aut’Creatifs are firm supporters of banning them altogether. However, it is not Aut’Creatifs’ mandate to take an official position on the subject.

That pesticides can cause neurological problems, and that some of these problems might be mistakenly equated with autism, all of that is possible. But that does not mean that that there is a cause-and-effect link between pesticides and autism. The joint report does not show any serious indication to that effect.

We therefore denounce what is another “fake news” item by which autistic people have been exploited for political and promotional purposes. We also want to disassociate ourselves from the alarmist discourse about autism contained in this report: ”alarming rise,” “deficits,” “undesirable problem,” etc. This kind of language stigmatizes autistic people and greatly harms their development and fulfillment. That, too, is a poison.

Antoine Ouellette, Lucila Guerrero, Mathieu Giroux, Stephan Blackburn, Lucie Latour

Le Conseil d’administration