Are There Risk Factors for Autism? A HealthCentral Explainer

ATsai Editor
  • Recent research has found risk factors for autism and Autism Spectrum Disorders (ASDs) that may shed some light on what contributes to the development of these disorders. In recent years, some people believed that vaccines with thimerosal, a mercury-containing preservative, increased risk for ASD. But that has been disproven by several studies. While parents should not be concerned about vaccinating their children, there are other risk factors to consider.


    How can the flu be a risk factor?

    A recent study published in the journal Pediatrics found evidence that having the flu during pregnancy, or a fever that lasts at least a week, increased the risk of giving birth to a baby who would be diagnosed with ASD before the age of 3. Researchers analyzed data from 96,736 children born in Denmark from 1997 to 2003. The mothers were asked questions about illnesses and antibiotic use during their pregnancies. The data suggests that having the flu during pregnancy doubles the risk of giving birth to a child with ASD, a fever lasting more than a week had three times the risk of giving birth to a child with ASD, and taking antibiotics while pregnant slightly increased the risk. 

    Add This Infographic to Your Website or Blog With This Code:


    Researchers concluded that more controlled studies are necessary. The lead researcher also noted that women who catch the flu or a have a fever during pregnancy should not be alarmed, as 98 percent of women who did have one of these ailments did not give birth to children with ASD.



                   [SLIDESHOW: 5 Reasons to Get the Flu Shot]



    What about parents with mental health issues?

    A July 2012 study looked at data from population registers in Sweden and Israel, and found that children who had parents or siblings who were diagnosed with schizophrenia or bipolar disorder had a higher risk of ASD.  Researchers found that children with parents who suffered from schizophrenia had three times the risk of developing ASD, while those with siblings with schizophrenia had about 2.5 times higher risk. Researchers also noted that the pattern for bipolar disorder was similar, but with less risk.


    Researchers concluded that ASD, schizophrenia and bipolar disorder likely share risk factors.


    Does age matter?

    It turns out age does matter, but more so for the father than the mother. Older fathers are more likely to pass on new mutations to their children than older mothers, according to a study published in the journal Nature. Researchers said that their findings could partially explain the link between autism and schizophrenia and other potentially hereditary conditions.


    Researchers studied the human genome, which is all the genetic data in a living thing. The human genome consists of about 3.4 billion sequences. The team gathered data on 78 families with children who had been diagnosed with schizophrenia or autism. The average age of the father was 29.7 years old. They then sequenced their genomes along with 1,859 other people as a comparison. The researchers found that for every extra year in a father’s age, there was a two-mutation per year rise in children. Researchers also identified the genetic characteristics associated with autism and schizophrenia.



                   [SLIDESHOW: 10 Warning Signs of Childhood Schizophrenia]



    What are the specific gene mutations?

    Another study published in Nature Genetics looked at specific gene mutations that lead to significantly enlarged brain size. Researchers found that these mutations were associated with a number of disorders, including cancer, epilepsy and autism. Researchers said that identifying the genetic causes of these diseases and developmental disorders could lead to new treatment possibilities.


    Does the immune system play a role?

    A July study found evidence to support the notion that specific changes in an overactive immune system can lead to autism, rather than just being a side effect. To begin the study, researchers injected pregnant mice with a viral mimic that triggered the same immune response that a virus would. This was based on previous research that found a correlation between viral infection during the first trimester of a human mother’s pregnancy and a higher risk of ASD.

    Add This Infographic to Your Website or Blog With This Code:


    Researchers found that the offspring of the mice who had been injected with the viral mimic displayed autism-related behavior symptoms, including decreased social interaction and problems with communication. Then, researchers looked at the immune system of these “autistic” mice and found that they had a number of immune changes, and some were parallel to immune changes seen in people with autism.


    The result of all the changes looked resembled an immune system in overdrive, which promotes inflammation. Researchers then wanted to test if the immune changes were responsible for the abnormal behavior in the offspring mice. The “autistic” mice were given bone-marrow transplants from typical mice. The stem cells from the typical mice replenished the immune system of the “autistic” mice and altered their behavior.


    Researchers pointed out that this method could not be translated to people at this time, but that the results suggest that targeting immune issues with innovative therapies in children could address behaviors associated with ASD.



    Christian Nordqvist. (2010, September 14). "Thimerosal (Mercury) In Vaccines Not Linked To Autism, New Research." Medical News Today. Retrieved from


    n.p. (2012, November 13). "Flu In Pregnancy Raises Autism Risk." Medical News Today. Retrieved from


    Petra Rattue. (2012, July 10). "Autism Risk Higher When Parents Have Schizophrenia Or Bipolar Disorder." Medical News Today. Retrieved from


    n.p. (2012, August 26). "Father's Age Linked To Risk Of Autism In Children." Medical News Today. Retrieved from


    Seattle Children's. (2012, July 3). "New Gene Mutations Found That Lead To Enlarged Brain Size, Cancer, Autism, Epilepsy." Medical News Today. Retrieved from


    Add This Infographic to Your Website or Blog With This Code:

    n.p. (2012, July 19). "Evidence Of Link Discovered Between Immune Irregularities And Autism." Medical News Today. Retrieved from


Published On: November 19, 2012