Wednesday, January 21, 2009

Simon Baron-Cohen Reiterates: Autism Results From Genetic AND Environmental Factors

Psychologist Simon Baron-Cohen of the Cambridge University Autism Research Centre has reiterated his previously stated position that autism results from the interaction of genetic AND environmental factors. In an exchange with a parent published on the One Click Group site Professor Baron-Cohen stated:

The One-Click Group seems to be a website for those who want to see more research into environmental risk factors in autism, and to me this seems to be a very worthy agenda. We know that autism is not 100% genetic in origin, since in the case of identical twins (who share 100% of their genes), there are instances of one twin having autism and the other not having it. In fact, the likelihood of the co-twin also having autism where one of them has it (in monozygotic (MZ) pairs) is about 60%. This means that there must be some non-genetic (i.e., environmental) factors that are part of the cause of autism. ...... I hope the above statement shows clearly and unambiguously that I regard autism as most likely the result of a gene-environment interaction.

Professor Baron-Cohen made the same point in a December 2007 interview piece published on TimesOnLine, Freedom of Expression:

Studies of twins have established that it is not 100 per cent genetic, since even among identical twins, when one has autism, the likelihood of both twins having autism is only about 60 per cent. This means there must also be an environmental component, but what it is remains unknown.

Professor Baron-Cohen's logic appears unimpeachable. Perhaps someone could convey the Professor's views to the US Department of Health and Human Services Interagency Autism Coordinating Committee (IACC) which decided to reverse its own recent decision to authorize funding research of potential environmental causes of autism, including vaccines. While they are at it perhaps they could also convey Professor Baron-Cohen's reasoning to the bloggers at the new ASAN media center at where they believe, as an article of faith, that autism is genetic.

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Anonymous said...

The 60% figure is for autism itself. Of the remaining 40%, 75% will be positive for an ASD,
that is, if one monozygotic twin has autism there is a 90% chance the other will have an ASD.

Both figures need to quoted.

Unknown said...


I quoted Simon Baron-Cohen as he articulated the point on two occasions. Assuming your unattributed data to be correct they still support the proposition that environmental factors cause Autistic Disorders AND ASD's.

Do you think research should be conducted to determine what environmental factors are involved?

Anonymous said...


Even if is true (what isn’t) that; “if one monozygotic twin has autism there is a 90% chance the other will have an ASD.” it still doesn’t mean that the Autism is genetically determined. At the moment it is not known why one sibling can be affected with autism and because of that it is not known how to protect other sibling.

Here is the link that put more light about monozygotic twin and autism.

if one twin is diagnosed with autism, the other twin has a 70-90% chance of having a similar diagnosis (Steffenburg et al. 1989, Folstein and Rosen-Sheidley 2001). The severity of the condition in identical twins, however, may differ considerably. (Bailey et al. 1995) In dizygotic (fraternal) twins, if one is diagnosed with autism, the chance of the other having a similar diagnosis is to 5-10%. Non-twin siblings of people with autism also have a 3-8% chance of having the same diagnosis, which is more than a 10-fold increase in risk compared to the general population. (Rutter et al. 1997)

In my opinion no one child is genetically predetermined to develop autism. Theories about genetically susceptibility aren’t product of science but are product of IntelliGENE- design-belief[/IntelliGENE Design Theory. Most of the gene theories are nonsense or a quackery based on a grain of science.

Luke Tunyich

Anonymous said...

The 60 % figure is probably from this study

A review of: Losh, M., Sullivan, P.F., Trembath, D., Piven, J. (2008). Current Developments in the Genetics of Autism: From Phenome to Genome. Journal of Neuropathology and Experimental Neurology, 67(9), 829-837. DOI: 10.1097/NEN.0b013e318184482d

The information that 75% of those with an "identical" twin with autism who don't have autism itself will have an ASD is from

Am J Psychiatry 161:539-546, March 2004

The study which showed the 60% concordance in monozygotic twins listed a 3-5% concordance for fraternal twins.

I'm not against looking at environmental factors. I don't expect that research will prove fruitful, but I'm not sure enough to leave than stone unturned

Stephanie said...

I watched a recent program on National Geographic about identical that was VERY interesting ( If anyone is interested in the genetics of identical twins (and the diseases they acquire and whatnot) than I highly recommend it as it gives a very good overview for the layperson. The website on it doesn't delve into the genetics of twins like the program did but if you can find the episode somewhere watch it.

Anonymous said...

Blah, blah, blah---not impressed with your intellectual posturing--Ever read the book, "How to Lie With Statistics"?---Pharmaceutical companies must keep it on the shelf by the good Scotch because they sure have perfected the art. The point is that you can intellectualize the problem till hell freezes over but you can never change the fact mercury is, among other biological horrors, a developmental neurotoxin! I don't care how many Phds you obtain it has always been an uncontionable evil with nation destroying repercussions to contrive to inject it in any amount into our beautiful children.