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Understanding the Causes of Autism Spectrum Disorder

Understanding the causes of Autism is where most parents and caregivers start the process of learning about autism. Even still, as parents, understanding the “why” behind autism can feel overwhelming. While research is ongoing, science has uncovered a few key causes, including genetics, and neurological factors that contribute to Autism Spectrum Disorder (ASD).

Definition of Autism Spectrum Disorder

First, a quick definition of Autism Spectrum Disorder (ASD). The CDC defines it as:

  • A developmental disability caused by differences in the brain.
  • Some people with ASD have a known difference, such as a genetic condition. Other causes are not yet known.
  • Scientists believe there are multiple causes of ASD that act together to change the most common ways people develop.

It is called a “spectrum” because every child’s abilities and challenges are unique—some may have strong language skills but struggle socially, while others may have delayed speech or need extra support with daily routines. New Centers for Disease Control and Prevention research states that 1 in 44 American children has been diagnosed with ASD and this ranges across all racial, ethnic and socioeconomic groups. Common signs include difficulties with eye contact, repetitive behaviors like hand flapping or lining up toys, and intense interests in specific topics. Many children with autism also process sights, sounds, and textures differently, which can make certain environments overwhelming.

When do Signs of Autism Begin?

The CDC goes to describe Autism symptoms beginning “before the age of 3 years and can last throughout a person’s life, although symptoms may change over time. Some children show ASD symptoms within the first 12 months of life. In others, symptoms may not show up until 24 months of age or later. Some children with ASD gain new skills and meet developmental milestones until around 18 to 24 months of age, and then they stop gaining new skills or lose the skills they once had.”

Causes of Autism Spectrum Disorder

Experts generally agree on these 5 main points when understanding the causes of autism.

There is No Single Cause

  • Autism does not stem from one single factor.
  • It develops from a combination of genetic and environmental influences.
  • Each child’s experience is unique.

“No simple theory of autism has ever panned out, and the scientific community has moved on from the search for a simple answer. Researchers now know that autism develops from a staggeringly complex interplay between genes and factors that can influence development in utero.” — Scientific American (Sept 10, 2025)

Genetic Factors

  • Research shows autism tends to run in families, suggesting a strong genetic link.
  • Specific gene variations are associated with increased likelihood of ASD.
  • Genetics do not “cause” autism on their own but may increase susceptibility when combined with other influences.

“We’ve successfully identified genetic causes of autism,” says Dr. Geschwind, Senior Associate Dean and Associate Vice Chancellor of Precision Health in the UCLA Health System and David Geffen School of Medicine at UCLA (DGSOM). “We’re now ready and moving into a new phase where we’re using the genetic information to develop therapeutics, and that’s very exciting.” — UCLA David Geffen School of Medicine (April 10, 2024)

Neurological Insights

  • Brain imaging studies reveal differences in how children with autism process information.
  • These differences can affect communication, social interaction, and sensory experiences.
  • Neurological pathways in the brain may develop differently, shaping how children perceive and respond to the world.

“There is new evidence that the cells responsible for communication in the brain may be structured differently in children with autism. Researchers at the Del Monte Institute for Neuroscience at the University of Rochester discovered that in some areas of the brain neuron density varies in children with autism when compared to the general population.” — University of Rochester Medical Center (October 9, 2024)

Environmental Influences

  • Maternal Health Conditions: Conditions like diabetes, obesity, and immune system disorders during pregnancy are associated with increased autism risk. 
  • Maternal Infections: Infections such as influenza, rubella, or other viral and bacterial infections during pregnancy can increase risk, potentially due to immune system activation. 
  • Advanced Parental Age: Both advanced paternal and maternal age at conception are associated with a higher risk of autism. 
  • Prenatal Exposure to Toxins: Exposure to substances like certain pesticides, air pollution, phthalates, and other chemicals during pregnancy may increase risk. 
  • Birth Complications: Complications leading to oxygen deprivation (hypoxia) or other trauma to the baby’s brain, extreme prematurity, and very low birth weight have been linked to increased risk. 
  • Medications: Use of certain medications during pregnancy, such as some selective serotonin reuptake inhibitors (SSRIs) and other drugs, is being studied for their potential contribution. 

Why Testing Matters

  • Early, accurate testing helps identify a child’s unique strengths and challenges.
  • The sooner autism is recognized, the earlier parents can access effective support and therapies.
  • Testing provides peace of mind and a roadmap for tailored care.

“In the 1980s, autism was diagnosed at a global rate of 6 per 10,000 people. Today that rate is 1 per 100 people. The Mayo Clinic’s Jessica M. Davis, M.D. attributes the recent increase in assessment and diagnosis to improved assessment networks, a wider understanding of autism and the availability of more-concrete information.” — The Mayo Clinic (February 18, 2024)

Recap

While there’s no single cause of autism, and understanding the genetic and neurological factors can help parents move forward with confidence, early testing is the first step toward unlocking a child’s potential. At the Life Change Group we provide comprehensive testing for autism for children which includes: clinical interview, sensory information diagnostic, multiple self reports, and testing with the ADOS-2 and/or the MIGDAS-2 (widely considered the gold standards for autism diagnosis).