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Autism: Environment Matters

By Lawrence D. Rosen, MD
For winemakers, it is widely accepted that it’s the “terroir” – literally, the ground but more figuratively, the overall environment - that matters.  In medicine, even Louis Pasteur supposedly admitted on his deathbed (in French of course), “Bernard was right; the Terrain is everything, the Germ is nothing.”  (source: http://www.mnwelldir.org/docs/history/biographies/louis_pasteur.htm).  The reference?  Claude Bernard, a 19th century French physiologist, believed that the host’s environment was just as important to the development of disease as the invading germs.  (source: http://en.wikipedia.org/wiki/Claude_Bernard)  
 
These debates about the cause of illness still rage today.  Most notably, the causes of autism remain as hotly contested as they are poorly understood.   Conventional wisdom holds that autism is predominantly a genetic disorder.  You are born with “bad genes” and that is that.  The holy grail for those supporting this theory has been research demonstrating that a vast majority of twins (more so with identical versus fraternal) shared autism diagnoses.  While genes certainly play a role in the development of autism, new research proves beyond a shadow of a doubt that the environment, in all its forms, has a major role to play as well.  In fact, it is the impact of a host of environmental factors on the expression of our genes that likely cause the majority of epidemic chronic illnesses plaguing our children today. (See The State of Children's Health)
 
Bernard was also a champion of the scientific method.   He noted, ”When we meet a fact which contradicts a prevailing theory, we must accept the fact and abandon the theory, even when the theory is supported by great names and generally accepted.” (source:  Bernard, Claude. An Introduction to the Study of Experimental Medicine, 1865. First English translation by Henry Copley Greene, published by Macmillan & Co., Ltd., 1927; reprinted in 1949.)  What are the facts now met with respect to autism?  This year, California scientists published a landmark autism twin study. 
 
The findings were best summarized by the New York Times:
 
In the new study, the largest of its kind among twins, researchers looked at 192 pairs of identical and fraternal twins whose cases were drawn from California databases. At least one twin in each pair had the classic form of autism, which is marked by extreme social withdrawal, communication problems and repetitive behaviors. In many cases, the other twin also had classic autism or a milder “autism spectrum” disorder like Asperger’s syndrome.  Identical twins share 100 percent of their genes; fraternal twins share 50 percent of their genes. So comparing autism rates in both types of twins can enable researchers to measure the importance of genes versus shared environment.  The study found that autism or autism spectrum disorders occurred in both children in 77 percent of the male identical twins and in 50 percent of the female identical twins. As expected, the rates among fraternal twins were lower: 31 percent of males and 36 percent of females.  But surprisingly, mathematical modeling suggested that only 38 percent of the cases could be attributed to genetic factors, compared with the 90 percent suggested by previous studies.  And more surprising still, shared environmental factors appeared to be at work in 58 percent of the cases.
 
The authors conclude, “Susceptibility to ASD has moderate genetic heritability and a substantial shared twin environmental component.”  Read that sentence again.  The importance of this statement cannot be overstated.  To date, millions of dollars have been devoted to unearthing a very small number of “autism genes.”  Some prominent scientists estimate that known genetic mutations associated with autism account for no more than 15% of diagnosed cases (source: http://www.childrenshospital.org/views/feb08/new_genetic_discoveries.html).   Continuing to try to prove a one gene – one disease hypothesis for autism is folly.  Research time and money should be devoted instead to better understanding the interactions between environmental factors and epigenetic expression.  We do have clues to examine.  Each day, new research is published elucidating environmental mechanisms associated with neurodevelopmental disorders.  Some of the environmental factors already linked to autism include heavy metals (lead, mercury, arsenic, manganese), pesticides (organophosphates, DDT), and polychlorinated biphenyls (PCBs).   (source: Landrigan PJ: What causes autism? Exploring the environmental contribution. Curr Opin Pediatr. 2010 Apr;22(2):219-25)  Author Dr. Philip Landrigan explains that in most of these examples, “environmental exposures relevant to autism appear to have occurred prenatally, indeed very early in the first trimester of pregnancy.”  The implication?  If we act now to limit exposure to these and other toxins, we may be able to prevent children from developing autism. 
 
 
Research into how these toxins disrupt human metabolism, including immune and nervous system functioning, will open crucial windows into environment-gene interactions.  We will ultimately be able to identify and modulate these environmental exposures – even in the presence of predisposing genes – to prevent the development of the observable clinical phenomena we call autism.   This is a much-needed, critical paradigm shift.   Only by identifying the mechanisms by which environmental factors influence genetic expression and resulting metabolic changes can we hope to reverse course and prevent the damage done.  
 
 
 
 
dr._rosen_2About Dr. Lawrence Rosen
 
Clinical Assistant Professor of Pediatrics, New Jersey Medical School; Chair, AAP Section on Complementary and Integrative Medicine;  Medical Advisor, The Deirdre Imus Environmental Health Center™.  
 
Dr. Lawrence D. Rosen is a board-certified general pediatrician committed to family-centered, holistic child health care. He is the founder of one of the country's first green, integrative primary care practices -- Whole Child Center (wholechildcenter.org) -- in Oradell, NJ. He serves as Medical Advisor to The Deirdre Imus Environmental Health Center™.
 
Dr. Rosen is a nationally recognized expert in Pediatric Integrative Medicine. He is a founding member and Chair of the American Academy of Pediatrics Section on Complementary and Integrative Medicine. He is appointed as clinical assistant professor in Pediatrics at UMDNJ/New Jersey Medical School. Dr. Rosen is a graduate of New York Medical College and the Massachusetts Institute of Technology. He completed his residency and chief residency in pediatrics at Mount Sinai Medical Center in New York. 
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