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Why Are Autism Spectrum Conditions More Prevalent in Males?

  • Simon Baron-Cohen mail,

    sb205@cam.ac.uk

    Affiliation: Autism Research Centre, Department of Psychiatry, University of Cambridge, Cambridge, United Kingdom

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  • Michael V. Lombardo,

    Affiliation: Autism Research Centre, Department of Psychiatry, University of Cambridge, Cambridge, United Kingdom

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  • Bonnie Auyeung,

    Affiliation: Autism Research Centre, Department of Psychiatry, University of Cambridge, Cambridge, United Kingdom

    X
  • Emma Ashwin,

    Affiliation: Autism Research Centre, Department of Psychiatry, University of Cambridge, Cambridge, United Kingdom

    X
  • Bhismadev Chakrabarti,

    Affiliations: Autism Research Centre, Department of Psychiatry, University of Cambridge, Cambridge, United Kingdom, Centre for Integrative Neuroscience and Neurodynamics, School of Psychology and Clinical Language Sciences, University of Reading, Reading, United Kingdom

    X
  • Rebecca Knickmeyer

    Affiliations: Autism Research Centre, Department of Psychiatry, University of Cambridge, Cambridge, United Kingdom, Department of Psychiatry, University of North Carolina–Chapel Hill, Chapel Hill, North Carolina, United States of America

    X
  • Published: June 14, 2011
  • DOI: 10.1371/journal.pbio.1001081

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How Increased Testosterone May Cause Autism

Posted by jamesmhoward on 10 Nov 2011 at 21:58 GMT

Regarding JAMA 2011 Nov 9;306(18):2001-10 "Neuron number and size in prefrontal cortex of children with autism"

I suggest the increase in prefrontal neuron number and size in autistic children are the effects of maternal testosterone. High maternal testosterone has been connected with autism in the literature.

It is my hypothesis that human evolution resulted from selection for testosterone: "Androgens in Human Evolution," Rivista di Biologia / Biology Forum 2001; 94: 345-362. (If your library does not subscribe to "Rivista ... ," you may read this at: http://members.cox.net/jm... . If you do not want to bother to visit this website, please, at least, note the chart from "General and Comparative Endocrinology" of 2003 which directly supports my explanation of human evolution. You may see the chart by going to the link above.)

The prefrontal cortex is larger in humans compared to the great apes. I suggest this is the primary result of the selection of higher testosterone in human females. That is, the increased maternal testosterone is the basis for our larger brains and its effects on subcranial differences between humans and the great apes. One aspect is increased prefrontal areas.

If maternal testosterone is high or high at inappropriate times, then, according to my explanation of human evolution, androgen receptors would increase in the fetal brain. Excess androgen receptors in the prefrontal cortex would increase the cell number and size.

My explanation of human evolution suggests that increased brain size causes a competition between the brain and the subcranial structures (body). Hence, as our brains increased in size, out bodies also started to differ from the great apes. Growth of the brain affects body growth.

If I am correct, then one should see competition within the brains of autistic individuals as a result of this competition. Problems with cerebellum formation and activity occur frequently within autistic individuals. I suggest this is due to increased androgen receptors within the prefrontal areas of the autistic brain which cause increased neuron number and size at the expense of the cerebellum. Growth of parts of the brain will affect other parts.

My work suggests that maternal testosterone periodically increases within the human population and, subsequently, creates problems. This is occurring at the present time. It is well known that autism is increasing, along with many other problems, simultaneously. A well known example is female breast cancer.

I suggest the foregoing explanation may explain the findings reported in JAMA. 2011 Nov 9;306(18):2001-10 "Neuron number and size in prefrontal cortex of children with autism."

James Michael Howard
Fayetteville, Arkansas

No competing interests declared.