Autism research has come a long way over the past several years, but researchers still haven’t determined an exact cause for Autism Spectrum Disorder (ASD). There’s a consensus among scientists that a number of influences are more likely at play, including biological, genetic and environmental risk factors.
What are some of the most common risk factors for autism?
Genes and Genetic Mutations
There’s no such thing as an “autism gene” – scientists haven’t linked one specific gene to all cases of ASD. That being said, there’s no shortage of research studies that link genes and genetic mutations with a higher risk of autism, but dozens of genes are known to play a role.
To date, researchers have tallied at least 65 genes that have a strong tie to autism, and over 200 more that have weaker ties to ASD. The list continues to grow. Just this year, a study revealed 18 more genes associated with autism. The more “high-impact” mutations appear to disable genes that are critical to early brain development.
Each case of ASD is unique, with its own combination of behaviors and developmental delays. With each new gene discovery, researchers are able to better explain the different cases of autism.
Centers for Disease Control and Prevention (CDC) data has shown that individuals with certain chromosomal conditions, like fragile X syndrome or tuberous sclerosis, are more likely to have ASD.
In addition to genes, there are some other biological factors known to play a role in the likelihood that a child will have ASD. One is paternal age – older fathers have been linked with higher autism risk. Siblings also play a role. Research from the University of California, Davis (UCD) found that children with at least one older sibling with ASD have an 18 percent chance of also having the disorder.
A number of environmental factors are also known to have an effect on autism risk. When it comes to the nutritional risk factors associated with ASD, the research on folic acid and omega 3 deficiency has been less conclusive. However, many individuals with autism have been shown to be vitamin-D deficient. Exposure to some pesticides and heavy metals, particularly mercury and lead, have also been linked with autism.
A meta-analysis study on the link between autism risk and prenatal influences revealed a number of pregnancy complications linked with ASD risk: advanced parental age at birth, maternal medication use during pregnancy, bleeding, gestational diabetes, and being born first rather than third or later.
A 2017 review found strong links between autism and certain traumatic birth complications, including hypoxia and ischemia. Babies with neonatal anemia, or being low on oxygen-carrying red blood cells, were found to be eight times more likely to develop autism later in life. Fetal stress caused by meconium aspiration, a condition in which oxygen deprivation leads a fetus to inhale waste products in the womb, was also linked to a sevenfold increase of later ASD development.