Advances in diagnostic capabilities and greater understanding and awareness of autism spectrum disorder seem to be largely driving the increase, the Rutgers researchers said. But there's probably more to the story: Genetic factors, and perhaps some environmental ones, too, might also be contributing to the trend.
The rates of autism are also rising because of changes in the way it's diagnosed. Currently, this is by measuring a child against known developmental benchmarks. One common assessment method is an 'Autism Diagnostic Interview – Revised': an interview between a trained assessor and the primary caregiver.
There are many different factors that have been identified that may make a child more likely to have ASD, including environmental, biologic, and genetic factors.
Having older parents, a difficult birth, or infections during pregnancy are all examples of factors that might increase the risk for having ASD. Beyond these factors, certain people are at higher risk than others. For example, ASD is four times more common in males than females.
Since autism is less prevalent in females, autism was always thought to be passed down from the mother. However, research suggests that autism genes are usually inherited from the father. One of the most common questions asked by parents of children with autism is which parent carries the autism gene.
Autism Prevalence
In 2023, the CDC reported that approximately 1 in 36 children in the U.S. is diagnosed with an autism spectrum disorder (ASD), according to 2020 data. Boys are four times more likely to be diagnosed with autism than girls.
Autism genetics expert Ivan Iossifov breaks down recent research that sheds light on how unaffected parents can pass autism onto their child. Parents with no history of autism in their families have a child who is diagnosed with the disorder. It's a common and upsetting story.
Advances in diagnostic capabilities and greater understanding and awareness of autism spectrum disorder seem to be largely driving the increase, the Rutgers researchers said. But there's probably more to the story: Genetic factors, and perhaps some environmental ones, too, might also be contributing to the trend.
Genetics. Genetic factors may be the most significant cause of autism. Early studies of twins had estimated heritability to be over 90%, meaning that genetics explains over 90% of whether a child will develop autism. This may be an overestimation, as later twin studies estimate the heritability at between 60 and 90%.
High levels of stress during pregnancy may also be connected to autism in children. This connection appears to have the most impact when the parent experiences stress between weeks 25 and 28 of pregnancy.
Key Autism Statistics & Facts
In 2023, the CDC reported that around 1 in 36 children in the U.S. is diagnosed with autism. Autism prevalence has increased 178% since 2000. The country with the highest rate of diagnosed autism in the world is Qatar, and the country with the lowest rate is France.
Autism is not an illness
It means your brain works in a different way from other people. It's something you're born with. Signs of autism might be noticed when you're very young, or not until you're older.
Autism is strongly genetic
The risk of having another affected child is estimated to be around 1 in 5. Family members of a person with autism also tend to have higher rates of autistic traits.
ADHD is not on the autism spectrum, but they have some of the same symptoms. And having one of these conditions increases the chances of having the other. Experts have changed the way they think about how autism and ADHD are related.
Prevention. There's no way to prevent autism spectrum disorder, but there are treatment options. Early diagnosis and intervention is most helpful and can improve behavior, skills and language development. However, intervention is helpful at any age.
Autism is likely to have multiple genes responsible rather than a single gene. However, it is not caused by emotional deprivation or the way a person has been brought up.
Autism doesn't get worse with age, but certain symptoms can become more pronounced and problematic as the child grows older and is more challenged.
“Firstborn offspring of two older parents,” Durkin's study noted, “were three times more likely to develop autism than were third- or later-born offspring of mothers aged twenty to thirty-four and fathers aged under forty years.”
The country with the highest rate of diagnosed autism in the world is Qatar, and the country with the lowest rate is France. Around 4 times as many boys have autism as girls. The rate of autism in the U.S. went from 1 in 150 in 2000 to 1 in 100 in 2022.
Autism is not caused by malnutrition or food-related challenges, but, for many people, there is a connection between autism and food. Research suggests that food-related challenges have a significant impact on many people who are diagnosed on the autism spectrum.
Children who have an older sister with autism are more likely to also have the condition than are those who have an older brother on the spectrum. The risk is higher among younger brothers than younger sisters.
Conclusion. Advanced grandparental age was associated with increased risk of autism, suggesting that risk for autism could develop over generations. The results are consistent with mutations and/or epigenetic alterations associated with advancing paternal age.
In the United States, prenatal genetic testing (PGT) for Autism Spectrum Disorders (ASD) is currently available via clinical genetic services. Such testing may inform parents about their unborn child's risk for ASD, prepare parents for the birth of an affected infant, and allow them to arrange for early interventions.