5 Top Theories About What Causes Autism

by Meg Kehoe

For years, scientists have researched possible causes of autism. Whether your child has autism or you're simply interested on the subject, knowing the top theories about what causes autism will help you to better understand the disorder and help refute anti-vaxxers argument that vaccinations may be the cause. (For the record, all research suggesting that vaccines cause autism has been discredited by the Centers for Disease Control and Prevention, in case you need extra points to share with anyone who might believe otherwise.) While research continues, Live Science noted that scientists believe there are a number of causes of autism, involving both your genes and your environment, or a combination of the two.

According to Rebecca Jones, Ph.D. and Assistant Professor Center for Autism and the Developing Brain & The Sackler Institute, there is no known single cause for autism. Though it is generally accepted that autism is caused by abnormalities in the way the brain is structured, or the way the brain functions, what causes those abnormalities is still up for debate. "It is likely that there are multiple cumulative factors that may increase the risk of a child developing autism such as genetics and the environment," Jones tells Romper in an interview.

The link between genetics and medical problems is a hot topic in the world of autism research. "In many families, there appears to be a pattern of autism or related disabilities, further supporting a genetic basis to the disorder," according to the Autism Society of America. "While no one gene has been identified as causing autism, researchers are searching for irregular segments of genetic code that autistic children may have inherited." Though no single cause has been identified, you can read on to find out the top theories of causes of autism.




"We know that genetics plays a role as there is an increased risk for autism in children who have an older sibling with autism," Jones says. For some children, autism can be associated with a genetic disorder. For others, genetic changes may make a child more susceptible to autism. "There is no single genetic mutation that causes autism, rather over a hundred genes have been implicated in increasing risk. However, the presence of one of these genes doesn’t necessarily mean that a child will develop autism, which is why we believe that the environment is an important factor as well. " Alycia Halladay, director of research for environmental sciences for Autism Speaks, told Live Science that about 20 genes have been identified as being linked to autism. And although the genes are located all over the human genome, according to Halladay, many have a role in brain development.


Brain Development


Flawed brain development is also a top theory in the causes of autism. According to the Medical Research Council, research over the last half century has established autism as a neurodevelopmental disorder. Though many signs point to brain development being a directly related to autism, the Medical Research Council stated that whether environmental factors have an impact on genetic susceptibility is still unclear.



Narong Jongsirikul/Fotolia

According to Dr. Alice Mao, a professor of psychiatry at Baylor College of Medicine, exposure to pesticides has also been linked to autism. Mao told My Health News Daily that some studies have found that pesticides can interfere with genes involved in the development of the central nervous system. Scientists believe that chemicals in pesticides may adversely effect those who are genetically predisposed to autism, which can lead them to develop a fully developed case of autism.




According to Autism Speaks, the use of prenatal pharmaceuticals is thought to be a potential cause of autism. Though use of prenatal pharmaceuticals was more widespread from the 1950s through the early 1970s, some prenatal pharmaceutical use still occurs today. Studies are currently searching for the neurological consequences that have been transmitted from generation to generation, and researches hope to gain a greater understanding of learning disabilities and autism, both of which may have links to prenatal pharmaceutical use.


Parental Age


According to a 2010 study published in Autism Research, women who are 40 years old have a 50 percent greater risk of having a child with autism than women who are between 20 and 29 years of age. And according to Jones, though the increase can be small, it is still there. Though researchers have not gained a solid understanding as to why parental age can influence the risk of bearing a child with autism, it is still one of the top theories of what may cause autism.