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.

Chromosomal Conditions

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.

Family/Biological Factors  

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.

Environmental Influences

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.

Prenatal Influences

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.

Birth Complications

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.