Though the exact cause of autism spectrum disorder (ASD) is not clearly understood, research suggests it often has a genetic component. This does not mean parents are to blame. Genetics are just one part of a very complex picture. Having a child with ASD is never the result of something you did or didn’t do, or something “wrong” with your genes.
Research findings can sometimes be inconclusive or identify variants of uncertain significance, which makes uncovering the root of ASD challenging. Still, here’s what we know so far:
What research has shown over time
In 1977, researchers introduced data showing ASD occurring in monozygotic twins (identical twins), offering an early look into a possible genetic link rather than earlier, controversial environmental explanations.
More recently, in 2019, researchers at Washington University School of Medicine found that the likelihood of ASD occurring in identical twins may be as high as 90%. They also noted that traits associated with ASD exist on a continuous spectrum. Differences in severity between identical twins are common, and the factors influencing severity may differ from those that contribute to ASD itself.
Additionally, SPARK, an ASD research group that conducts genetic testing, notes “Autism differs from other genetic conditions that may involve a change to a single gene or chromosome.” Their researchers have identified hundreds of genes that may play a role in ASD, which means there is no single gene responsible for the condition. For this reason, genetic testing often looks for patterns rather than one definitive cause.
Fragile X syndrome
Fragile X syndrome (FXS), however, is a single-gene disorder commonly associated with ASD, accounting for up to an estimated 6% of all individuals with ASD. FXS results from a mutation of the FMR1 gene on the X chromosome, which prevents the production of a protein called FMRP needed for typical brain development. It affects both boys and girls, but a co-occurring ASD diagnosis is currently understood to be more common in boys.
FXS can be diagnosed through a blood test. Identifying FXS can help explain intellectual or behavioral challenges and guide care planning. For more information about FXS, visit the National Fragile X Foundation.
Rett syndrome and other conditions
Rett syndrome (RTT) is another single-gene disorder often associated with ASD. Unlike FXS, RTT occurs due to a random mutation in the MECP2 gene rather than being inherited. RTT primarily affects girls, and individuals may show traits similar to ASD or even receive an ASD diagnosis before RTT is identified.
Similarly, other genetic conditions may also present with ASD traits, such as:
- Landau-Kleffner syndrome
- Phelan-McDermid syndrome
- Angelman syndrome
- Williams syndrome
- Prader-Willi syndrome
- Tardive dyskinesia
Treatment for these conditions may differ, even when symptoms overlap. Genetic testing can help clarify these distinctions and guide care.
Benefits of genetic testing
Families choose genetic testing for many reasons. It’s important to know that genetic testing for ASD is not used for diagnosis and is typically recommended by a pediatrician or specialist.
Genetic testing is not about finding something “wrong” or changing who a child is. Instead, it provides insight into how a child develops and can help guide care and support. In some cases, results may connect families to research opportunities or clinical trials, creating pathways to additional resources and community connections.
Even without providing a clear cause for ASD, genetic testing can offer meaningful information. It may reveal co-occurring medical or developmental concerns, such as epilepsy or intellectual disabilities, that require monitoring or early intervention. It can also help families understand hereditary factors and recurrence risk, which is valuable for future family planning.
Variance in autism presentation
Because ASD is shaped by a complex mix of genetic factors, every child’s experience is unique. These variations can influence how traits appear and the degree to which they impact daily life. Some children may face learning challenges, while others excel academically but find communication or social interaction difficult. Genetic testing can help families understand these differences, identify related health concerns, and plan care that meets each child’s individual needs.
Common signs of ASD may include:
- Not responding to their name
- Resistance to physical touch
- Preference for playing alone
- Limited eye contact or facial expression
- Delayed or atypical speech patterns, or being nonverbal
- Repeating words or phrases verbatim
- Difficulty understanding simple questions or directions
- Trouble expressing emotions or recognizing others’ feelings
Unusual approaches to social interaction, such as being passive, aggressive, or disruptive
Difficulty interpreting nonverbal cues and body language
Is ASD genetic? Research continues to show that it is influenced by many factors, and no single gene or decision necessarily determines an outcome. For many families, enhanced genetic testing can lead to greater understanding and preparation, while for others it may provide assurance for themselves and others. Families also deserve reassurance that ASD is not anyone’s fault, it is simply part of human diversity.
If you’re concerned your child may have ASD, start by talking with their pediatrician. They can explain what a diagnosis means and connect you to resources. Share with them the behaviors you’ve noticed, review age milestones, and bring questions to guide next steps like behavioral testing.
Maxim Behavioral
Please note: Maxim Behavioral does not conduct the formal assessments and evaluations required to diagnose ASD; however, we can support families after a diagnosis with personalized applied behavior analysis (ABA) care.
We recognize the individuality of every child and family, and we are committed to supporting differences with compassion, understanding, and care. For more information about ABA services available in your area, contact your local Maxim office.
