Last week, I discussed the fact that Autism rates have tripled. It is not clear whether this is due to better detection and reporting or an increase in the number of Autism cases.
There is no known single cause of autism spectrum disorder (ASD), but it is generally accepted that it is caused by abnormalities in the brain structure or function. Brain scans show differences in the shape and structure of the brain in children with ASD compared to neurotypical children.
We do know that genetic factors may be the most significant cause for ASD. Much of the risk of developing ASD, around 83% according to one analysis, comes from inherited genetic factors. A child can inherit risk factors from one parent or both. Early studies of twins had estimated heritability to be over 90% meaning that genetics explains over 90% of whether a child will develop ASD. Researchers estimate that 2,000 to 3,000 genes contribute to ASD.
Much has also been written about environmental factors or influences. These influences appear to increase the risk that a child will develop ASD. However, it is important to keep in mind that increased risk is not the same as cause.
Other factors may include:
- A child’s sex. Boys are about four times more likely to develop ASD than girls are.
- Their disorders. Children with medical conditions such as fragile X, tuberous sclerosis, Rett syndrome have a higher-than-normal risk pf ASD or autism like symptoms.
- Extremely preterm babies. Babies born 26 weeks before gestation may have a greater risk of ASD.
- Parent ages. There may be a connection between children born to older parents, but more research is necessary to establish this link.
One of the greatest controversies in ASD centers on whether a link exists between the disorder and childhood vaccines. NO reliable study has shown such a link. The original study that began this debate was retraced due to poor design and questionable research practices.
I hope that my brief review has helped you better understand the causes and risk factors of ASD.