Sunday, June 29, 2008

Environmental Causes of Autism and the Existence of an Autism Epidemic

If you can believe some professors of cultural anthropology and classical literature there are no environmental causes of autism and there is no autism epidemic. ALL of the dramatic increases in the numbers of autistic children and adults are due ENTIRELY to the definition changes in the DSM and to diagnostic substitution. Bringing their powers of personal opinion, societal observation and literary analysis to bare on the subject they have concluded that there is no autism epidemic.

We can all rest easy now that the rumor of an autism epidemic has been thoroughly discredited by these uh .... giants of science. No need at all for parents to worry about mercury, lead, pesticides and other harmless substances to which we as DNA bearing parents or our children themselves might be exposed. We can all rest assured that autism is purely genetic. Any and all increases in cases of autism must be due entirely to definition change, diagnostic substitution, increased awareness etc. According to the true believers autism has only genetic causes and there is nothing we can do to treat or cure our autistic children. Que SerĂ¡ SerĂ¡.

Of course there are heretics out there, unbelievers who have not yet seen the light, people who actually give credence to theories about global warming. People who are concerned generally about the increasingly toxic bath into which each new generation is born. I must confess to being one of those heretics. While the genetic bases of autism are becoming known with increasing specificity the role of possible environmental cause or triggers of autism has not been eliminated. Far from it.

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.

Simon Baron-Cohen, Freedom of Expression, TimesOnLine, December 14, 2007

A recent article in Pediatrics, Official Journal of the American Academy of
Pediatrics, by authors Bruce M. Altevogt, PhD, Sarah L. Hanson, BA and Alan I. Leshner, PhD also addresses the mix of genetic, biological and environmental stressors. All three authors are members of the Forum on Neuroscience & Nervous System Disorders, Institute of Medicine, Washington, DC. Dr. Leshner is also associated with the American Association for the Advancement of Science, Washington, DC. In the abstract for Autism and the Environment: Challenges and Opportunities for Research, PEDIATRICS Vol. 121 No. 6 June 2008, pp. 1225-1229 (doi:10.1542/peds.2007-3000) , it was stated that:

Autism spectrum disorder is a complex developmental disorder that dramatically affects the lives of patients and their families and the broader community. The causes of autism are unknown; however, evidence increasingly suggests that a complex interplay among environmental stressors, genetic mutations, and other biological factors likely plays a significant role in the development and/or progression of autism spectrum disorder. [bold highlighting added - HLD]

In Environmental Factors and Limbic Vulnerability in Childhood Autism American Journal of Biochemistry and Biotechnology 4 (2): 183-197, 2008 Dr.Richard Lathe of Pieta Research, Edinbugh, expressly argues against diagnostic substitution as a complete explanation for the current prevalance of autism spectrum disorders and stresses the likelihood of substantial environmental contributions:

The rise in prevalence of autism spectrum disorders (ASD) is suggestive of a
new etiology. Diagnostic substitution alone is unlikely to account for the increase, while genetic association with detoxification gene alleles points to an environmental contribution. Subtle structural anomalies in the ASD brain are widespread but limbic damage seems important for the development of behaviors diagnostic of ASD. The limbic brain is especially susceptible to environmental challenge: internal sensing, physiological feedback and neuroinflammatory processes may underlie this sensitivity to insult. Primary damage leading to ASD in later life is likely to take place in utero and/or in the immediate postnatal period. Despite evidence of heavy metal involvement, a causal connection may not yet be concluded because subjects exposed to metals tend to be exposed to other environmental agents. Because maternal minerals and lipids are supplied to the unborn child, historic toxic exposure of the mother may be pivotal. A two-hit combination of genetic susceptibility and environmental challenge is argued to underlie the rise in ASD.

Personally, I believe that we are in the midst of an Autism Knowledge Revolution in which science, not the ancient Greeks, or superficial and irrelevant cultural comparisons, will determine with increasing certainty the causes of autism, be they genetic, environmental or some combination of factors. As that knowledge increases debates about whether we are living in an autism epidemic should also be decided with greater certainty.


jonathan said...

Hi HD, did you see Steve D's posts attacking you for posting this? Hopefully you will go over to the one dad's opinion blog and straighten him out. Thanks, Jon Mitchell

Unknown said...

Thanks jonathan

I have now visited and responded.