Autism is a relatively common childhood disorder as it affects over 2.7% of children in the United States. However, the cause of autism remains highly elusive for researchers.
In trying to understand what brings about autism spectrum disorder (ASD), it is important to distinguish between causes and risk factors. Causes are external events or biological factors that cause a child to develop ASD symptoms. To determine specific causes, scientists need to control experiments and conduct random controlled trials (RCT’s). To date, there have been no studies of this kind that have demonstrated a cause of autism in a controlled manner.
Despite this lack of direct causal connection, there have been significant advances in understanding the risk factors associated with ASD. It is unclear how these risk factors are associated with ASD as many people have these factors but do not express symptoms of ASD. Nevertheless, it is diagnostically and therapeutically important to understand these factors in helping children with autism spectrum disorder. These risk factors fall into 2 major categories: genetic and environmental:
The heritability of ASD has varied in the literature, but a more recent large scale study estimated the genetic component to account for over 50% of the variance in ASD.
Even with this evidence, researchers are still unable to link genetic variants to the expression of the disorder.
- Older maternal age at conception: A child born from two older parents is 3x more likely to develop autism than were third- or later-born offspring
- Prenatal exposure to chemicals in pollution and pesticides
- Maternal health risk factors such as obesity, diabetes, or immune system disorders
- Birth complications such as very low birth weight, extreme preterm birth, multiple pregnancies, oxygen deprivation
In any discussion of the causes of ASD, it is important to note that scientists and researchers continue to find that vaccines do not cause autism. A user-friendly summary of this research can be found here.