Extreme Male Theory of Autism

Tuesday, June 30, 2009 at Tuesday, June 30, 2009
I have debated whether or not to approach the topic of Autism. After reading a recent article, I decided to broach it. I must preface this entry by saying that I do not study Autism, but it is definitely a very hot topic of study and research in the Neuroscience community. There have been quite a few theories presented as an explanation for why and how Autism is “caused”. As with any other disease or limitation of the brain, there are probably a host of reasons and causes for any one particular disease. This is very challenging for Neuroscientists, doctors, etc because it impacts our/their ability to find the most optimal rehabilitation or cure. On the other hand, the complexities of these various ailments of the brain just go to show how marvelous and intricate our brain is!

Autism is classified as a Pervasive Developmental Disorder. There are a variety of symptoms that typically appear before the age of 3. Symptoms are (but not limited to) impairments in social interactions, language development, repetitive behavior and limited interests. There is definitely a known genetic cause of Autism, however, whether or not it is caused by genetic mutations or a combination of “faulty” genes is unclear. There has been a recent surge in groups adamant that vaccines cause Autism. While I respect that these groups have some convincing evidence, overall this theory just doesn’t hold water when you look at the majority of scientific data from studies. Now before I go and piss off all of those who feel that vaccines have a strong correlation to Autism, I must remind everyone that correlation DOES NOT equal causation. Just because something is correlated, does not mean you can assume it has any real part in causing the ailment. However, I do feel that we probably over-vaccinate and the groups that try to link a correlation between vaccinations and Autism have definitely highlighted this point.

I just read an article that touched on a chemical exposure theory to Autism. This, in addition to a genetic predisposition, is probably a good summation of what contributes to the onset of Autism. The article was written by Harvey Karp, an Assistant Professor of Pediatrics at UCLA and (for all you Moms out there) the author of “The Happiest Baby”. The rational he presents in his article is pretty darn convincing. Here is the summation: our households are being invaded by a number of chemicals like formaldehyde, fire retardants, bisphenol A (BPA-an organic compound present in plastics), phthlates (substances added to plastics to increase durability, flexibility), etc. These little chemicals are known as known as endocrine disrupting chemicals (EDCs). “These substances are the focus of intense scrutiny because: 1) they're found in every home in America 2) they're increasingly linked to human disease 3) our exposure to them has risen in parallel with the surge in autism diagnoses and 4) they may theoretically affect the developing fetal brain” (Karp). In both humans and animal studies, EDC’s have been linked to a variety of health ailments including cancer, interruption of reproductive function and other hormone-related disorders. In 1996, Clinton and Congress designed tests and ordered the Environmental Protection Agency (EPA) to test various chemicals that were suspected to be EDC’s. However, when Bush came into office, testing was stopped and the law ignored. According to Dr. Harp, “our exposure to EDCs is no mere theoretical concern. In 2000, a Centers for Disease Control (CDC) study found detectable phthalates in 99.9% of adults including women of childbearing age. The CDC also discovered detectable levels of BPA in 93% of thousands of Americans tested (6 years of age and older)”.
A major concern is that these chemicals are found in women of childbearing age. Therefore, it is only logical to conclude that these chemicals could be passed from a pregnant woman to her fetus, and thus affect the developing brain. So now we introduce the “extreme male theory” of Autism. The theory is based on the premise that boys are approximately 4 times more likely to have Autism than girls. If something occurs, like exposure to one or an accumulation of many EDC’s, the effect may be over-masculinization of the brain. According to Karp, this theory is supported by 2 pieces of evidence: 1) elevated exposure to testosterone in utero results in a heightened male-type behavior (i.e. impaired language development) and 2) male and female autistic children show heightened male characteristics like impaired social and language development. EDC’s can cause masculinization in utero.
I am not suggesting that this “extreme male theory” is the end-all-be-all, but the evidence and research is pretty disconcerting. I do think we can go overboard and become too worrisome about trace level of chemicals. However, I personally work with formaldehyde and I can tell you that we take A LOT of precautions to limit our exposure as much as possible. It is a known carcinogen. So if adult exposure is harmful, surely exposure in utero, infancy or childhood is deleterious.

As a side note, concern over both BPA and phthalates has risen in both America and Europe and are being phased out of many products. In fact, I only buy BPA and phthalates-free products for my son.



  1. a Says:

    I don't know if I fully understand the "extreme male-ness" of this theory. I follow the chemical connection - it can potentially wreak quite a bit of havoc on the developing brain. But what exactly is the connection of these chemicals to heightened male-type development? And why are these things deemed "extremely male"?

    When I was interviewing and talking to lots of people about a lot of things I know very little about (including autism, as I was considering this as my future focus), an interesting idea was brought up by a couple of researchers studying autism or related topics. Basically, there's increasing evidence and they're starting to look at contributing factors of the father on risk for autism. One of those things is the age of the father - there's lots of evidence apparently to support the hypothesis that the older the father, the more at risk the child is for autism (when combined with the myriad other risk factors, of course). They've even done an animal study where they bred mice (or rats, don't remember) with mothers of the same age, breeding experience, etc., with males of varying ages. The rodents in the litters sired by older males had higher rates of autistic-related impairments in their social behavior, learning, and general rodenty well-being. Thought that was pretty interesting.

    It's just one of those really tough things - there's likely a genetic component, very likely many environmental components (including chemicals in the environment), and some very complex interactions between all of these factors. It'll be hard for researchers in this area to pinpoint causes very accurately for a long time I think. (Incidentally, Eric Courchesne at UCSD is doing some really neat in this area.)

    Sorry for the super duper long comment - enjoyed reading your post and will definitely keep up with it! :)


  2. Pam Says:

    Certainly makes you think. For a while as a nation we were all about "better living through chemistry." Both the chemical component (do vaccines count as chemical exposure?) and the age of the father are ineresting and will be fascinating to see how that research progresses.

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