Environment May Be as Important as Genes in Causing Autism
Wednesday, July 06, 2011
Health experts have gone from blaming mothers to singling out genetics for causing autism in children, to now giving considerable weight to environmental factors as potential causes.
A few decades ago, therapists attributed autism to a lack of maternal warmth. More recently, scientists said the condition was entirely a product of genetics. This week, a new medical study was published that says environmental influences, including conditions in the womb, may be just as important as genes with regards to autism, which is affecting at least 1% of those living in the developed world.
Autism is a neural disorder characterized by impaired social interaction and communication, and repetitive behavior. Signs usually appear in a child before the age of 3.
"We've known that genetics played a huge role. The surprise was that the environmental factors have been underestimated," said Clara Lajonchere, vice president of clinical programs for Autism Speaks, a group that helped fund the twin study.
After examining 192 autistic pairs of identical and fraternal twins, researchers at Stanford University concluded 38% of the cases could be attributed to genetic factors, while shared environmental factors appeared to be the cause in 58% of the cases.
The same journal that published the Stanford study also produced an article that pointed to certain antidepressants as a possible cause for autism. The culprits in these cases were so-called SSRI’s like Prozac, Zoloft, Celexa and Lexapro.
But the researchers of the second study added that the risk of antidepressant-related autism was quite low—about 2%.
A 2009 study in Calfornia found that the incidence of autism had increased there seven-fold since 1990 and pointed a finger at environmental factors. Scientists conducting that study cited potential factors that babies and fetuses are exposed to, including pesticides, viruses and chemicals in household products. They advocated for a sharper focus on the environment by researchers.
As scientists turn their attention to the environment, they are finding no shortage of potential culprits. One study found that mothers of autistic children were twice as likely to use pet flea shampoos. Another found a link to phthalates, a compound found in vinyl and cosmetics. Dozens of substances, including lead, mercury, brominated fire retardants, PCBs and pesticides are known to alter the way the brain grows.
However, one suspect was recently removed from most people’s list: vaccines. A 1998 study by Andrew Wakefield that drew a lot of interest and ardent supporters by proclaiming a solid vaccine-autism link was attacked for years before finally being debunked in a January British Medical Journal article as a fraud.
-Noel Brinkerhoff, Ken Broder
New Study Implicates Environmental Factors in Autism (by Laurie Tarkan, New York Times)
UCSF, Stanford Autism Study Shows Surprises (by Erin Allday, San Francisco Chronicle)
Autism Increase Not Caused Only by Shifts in Diagnoses; Environmental Factors Likely, New California Study Says (by Marla Cone, Environmental Health News)
Wakefield’s Article Linking MMR Vaccine and Autism Was Fraudulent (by Fiona Godlee, Jane Smith and Harvey Marcovitch, British Medical Journal)
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