Is There an Autism Epidemic?
Autism diagnosis rates have risen over the past two decades—but why? An autism researcher explains what's behind the increase.
Over the past 20 years, autism diagnoses have increased by about 300%, says Christine Ladd-Acosta, PhD, vice director of the Wendy Klag Center for Autism and Developmental Disabilities.
It’s a big number, but does that mean we’re seeing an autism epidemic? And what is behind that increase?
In the May 15 episode of Public Health On Call, Ladd-Acosta, an associate professor in Epidemiology, joined host Josh Sharfstein, MD, to discuss a new report about the number of children diagnosed with autism and what this research shows—and doesn’t show. This Q&A is adapted from that conversation.
How is autism defined?
When we use the word autism, we're actually talking about Autism Spectrum Disorder (ASD). The key word is spectrum because it truly is a wide range of symptoms and challenges that these children and adults experience in their lives.
Over the past two decades, the definition has broadened to include some conditions that used to have specific diagnoses attached to them, such as Asperger's Syndrome or Pervasive Developmental Disorder. They now fall under this broader ASD umbrella.
How do you monitor rates of autism?
We need to understand who in our community has autism to better understand their needs. As part of that, I've been fortunate to be part of the Maryland Autism and Developmental Disabilities Monitoring (MD-ADDM) network. We contribute to the overall CDC numbers that come out every two years on the number of kids in our communities who have been identified with autism.
In Maryland, we work closely with health and educational partners. We collect information from their records and review that information to determine how many children in their systems meet the criteria for an ASD diagnosis. We share those numbers with the CDC, which conducts an overall analysis across all the sites that are part of the ADDM network.
What were the findings for the latest report in Maryland?
CDC’s latest report found that 1 in 31 8-year-old children was identified with autism across ADDM’s 16 sites. Here in Maryland, we found that 1 in 38 8-year-olds were identified with autism.
Compared to 20 years ago, we're now seeing more children identified with autism who identify as Black, Asian, and Pacific Islander than white. We used to think primarily white boys were impacted by autism, but now we see it's all of us—many of our communities have children with autism in them—and not just boys. Over 1% of girls are identified with autism.
So, we know the number of children identified with autism is increasing.
There has been a nearly 300% increase over the past 20 years, but if you look at any two-year period across the sites that are monitoring the number of children identified with autism, it’s somewhere between a 10%–20% increase every two years.
What's behind this increase?
There are two main reasons for the increase. The first is the broadened definition of Autism Spectrum Disorder, which means that more people are meeting this definition now than previously.
Second, there have been many widely successful public health programs that increased screening at wellness visits for children ages 18–24 months to look for signs of autism. Parents, caregivers, and community members are also more aware of the symptoms, and autism is being more accepted in the community. People are not as afraid to seek help and know where to go when they have concerns.
There are concerns that the increase in autism diagnoses is because something is causing more children to be affected by the condition. Is this accurate?
Changes in the diagnostic criteria and increased screening at wellness visits seem to be the main contributors. There have been a few studies over the past two years that have looked at a specific subgroup of individuals on the spectrum who frequently need 24-hour-a-day support and care from a caregiver, often have very limited verbal communication skills, or have intellectual disability that co-occurs with autism.
The data has shown that rates of autism for that subgroup have increased minimally, if at all, over the past nearly 10 years.
Rates have increased the most for individuals who are not in that subgroup, who may have more subtle phenotypes and fewer significant co-occurring conditions. We think this is most likely due to our ability to identify these subtle traits and symptoms better.
We sometimes hear the phrase “epidemic of autism.” How do you feel about that term?
When I hear the word epidemic, I think of a quick, immediate increase in many individuals who have a certain condition. We’re not seeing that with autism. What we are seeing is a gradual rise over the past 20 years due to broadened diagnostic definitions, better screening, and increased awareness.
There are still a large number of people in our community with autism, and our focus should be on getting them the services they need to lead healthy lives and reach their full potential.
This interview was edited for length and clarity by Rin Swann.
