Environmental connections to public health >>
So what really causes autism?
Special to Enviroblog by Sonya Lunder, EWG Senior Analyst
If you follow scientific news on autism, then you've probably noticed frequent reports of new discoveries of genes "linked" to the "disease."
While an estimated 130-something genes have been linked to autism, last week week's report in Medical News Today about "genes" that cause autism, was slightly more dramatic than the rest. More than a dozen researchers surveyed the genetic codes of about 10,000 people, many with autism, and discovered that a genetic variant in a region of the genome that governs brain connectivity is more common in people with autism.
Are genes a promising lead? Perhaps... For those of us eager for a cause and a cure, the wait isn't over. The genetic variant reported by the researchers was found in 65 percent of patients with autism but also 60 percent of those without the disorder. The researchers estimate that these genes or variations account for 15 percent of all autism cases. However someone whose genetic code contains this pattern has just 20 percent increased risk of autism.
The most promising aspect of this discovery is that it is likely to lead to further research. Environmental factors may pull the trigger Most everyone who studies autism acknowledges that many genes play a role in the disorder but that environmental (or non-genetic) factors likely trigger the disease in susceptible people. Those following the elusive hunt for the environmental factors that trigger autism have amassed an eclectic list of possible factors.
Some environmental causes of autism?
- Childhood television-watching and possibly rainy weather. Confusing, eh?
- Vinyl floors in the bedroom evidently doubled the risk of autism in Swedish children, compared to those whose bedrooms have wood or linoleum.
- Having an "older" mother or father -- meaning moms over 35 and dads in their 30's or 40's and older.
- Breech birth, but scientists themselves have no idea how autism might cause a baby to be positioned head-up at delivery or how position in the womb could cause a healthy baby to become autistic.
- Stress during pregnancy. Stress...an unavoidable aspect of daily life. Perhaps the most dubious claim for the causes of this epidemic.
This list is incomplete, slow to emerge and quite unsatisfying. Like genes, there may be a host of environmental stressors that trigger autism. But I think we need to look a little harder. What relatively recent developments across our society may stress the developing brain and other systems of a fetus and young child? What about oxidative stress? EWG scientists are intrigued by a study by researchers at the University of Arkansas for Medical Sciences that shows that children with autism have abnormal response to oxidative stress.
This pattern could be affected by a variety of genes that govern the body's ability to quickly produce antioxidants in response to external stresses. And a long list of environmental exposures--from air pollution to pesticides--would be more challenging for children whose genes make them vulnerable to oxidative stress.
Maternal stress and breech births have been around for ages. Let's get funding flowing to look for other factors that can prevent this devastating disease from affecting the next generation.