Could Some Forms of Autism Actually Be Caused By the Environment?

First they blamed the moms.  Then they blamed the vaccines.  Now research is showing that some cases of autism spectrum disorder (ASD) may actually be environmentally-caused.

The findings, according to newswise.com, "shed light on why older mothers are at increased risk for having children with ASD and could pave the way for more research into the role of environment on ASD."

 The U.S. Centers for Disease Control and Prevention announced in March that one in 68 U.S. children has an ASD—a 30 percent rise from 1 in 88 two years ago. A significant number of people with an ASD have gene mutations that are responsible for their condition. But a number of studies—particularly those involving identical twins, in which one twin has ASD and the other does not—show that not all ASD cases arise from mutations, the Web site reports. 

Other studies have shown that genes may only be responsible in half  the cases of ASD diagnosed, newswise notes.  Media reports on the causes of ASD have focused on the fact that older fathers (40 and over) are more likely than younger fathers to have children with an ASD, probably because of gene mutations that accumulate over the years in sperm-making cells.

Yet older mothers (35 and over) face a similar risk that is entirely independent of their partners’ age. But for older mothers, scientists know very little about why this risk exists. The Einstein researchers looked for genetic as well as environmental influences that might account for older mothers’ increased risk for having children with ASD.

Researchers swabbed the cheeks of children with ASD.  Cheek cells can show environmental and gene differences.  Since the eggs of older mothers are prone to having abnormal numbers of chromosomes, the researchers first analyzed the cells for abnormal chromosome numbers as well as other chromosomal defects that might account for ASD. No such problems were found in the cells of ASD or typically developing (TD) children. 

“If environmental influences were exerted during embryonic development, they would encode a 'memory' in cells that we can detect as chemical alterations of genes,” newswise quotes lead author John Greally, M.B., B.Ch., Ph.D., of Albert Einstein College of Medicine. "“Genes interact with each other to create molecular pathways that carry out important functions,” said Dr. Greally. “Our findings suggest that, at least in some individuals with an ASD, the same pathways in the brain seem to hit by both mutations and epigenetic changes. So the severity of someone’s ASD may depend on whether or not a gene mutation is accompanied by epigenetic alterations to related genes.”

In other words, it's quite possible that some forms of ASD may be caused both by gene mutations and certain environmental stressors.  





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