How Common Is Autism?

The clinical term for autism is autism spectrum disorder (ASD). It’s a neurodevelopmental disorder, and you’re born with it. Changes in the brain cause autistic people to learn, behave, communicate or interact differently from what’s typical for most people — who are often described as neurotypical.

“It really is a spectrum,” says developmental pediatrician Carrie Cuffman, MD. “No two people with autism are alike.” And that can make identifying the condition tricky.

Even so, ASD diagnoses are on the rise. Dr. Cuffman explains why.

Why have autism diagnoses increased?

Autism diagnoses have gone up all around the globe over the past 20 years.

The most recent research from the U.S. Centers for Disease Control and Prevention (CDC) found that 1 in every 31 children in the U.S. has ASD. They also found that boys are three times more likely to get a diagnosis than girls.

That’s a big increase. But it’s not a sign of an “autism epidemic.” It’s possible there’s been a slight increase in the number of autistic people. But most of the growth is due to changes in ASD diagnosis and treatment.

Increased awareness

In many ways, the rise in ASD diagnoses is good news. It means awareness has gone up.

“You’re much more likely to ask your kid’s providers about autism when you know what it is,” Dr. Cuffman explains. “We’re diagnosing more kids — and doing it earlier than we used to.”

And children aren’t the only ones benefiting. Many adults who never got tested as kids are finally getting diagnosed now, too.

Accommodations

It’s not just public awareness fueling the uptick in ASD numbers. It’s also the fact that an ASD diagnosis can be helpful now, in ways it wasn’t in the past.

“More services are available now,” Dr. Cuffman notes. “It’s worth getting your kid diagnosed because there are more treatment options out there that you can access.”

We’re talking speech and language therapy. Social skills groups. Specialists in developmental nutrition and psychiatry. There are lots of supportive services to help autistic children thrive. And many of them either didn’t exist before or weren’t easy to access.

“Parents wouldn’t bother to have their kids evaluated because there weren’t accessible treatments,” Dr. Cuffman says. “Now, a diagnosis means you’re more likely to get help for a child who can benefit from it.”

Changes to the diagnostic criteria

ASD cases are also up because what counts as ASD has changed.

The Diagnostic and Statistical Manual is the American Psychiatric Association’s (APA) reference text. The book classifies and explains the diagnostic criteria for all mental health and brain-related conditions.

Before the 2013 edition (the DSM-5), ASD didn’t exist. Instead, there were four different developmental disorders doctors had to choose from:

• Autism
• Pervasive developmental disorder
• Asperger’s syndrome
• Childhood disintegrative disorder

It was, in a word, confusing. And the diagnoses were mutually exclusive: Doctors needed to choose the one diagnosis that was the best fit, even if a child had symptoms of all four.

The same was true of attention-deficit/hyperactivity disorder (ADHD). You couldn’t diagnose somebody with ASD and ADHD.

The result? Lots of misdiagnosed, undiagnosed and underdiagnosed kids. These rules had a particularly negative impact on girls, kids with mild ASD symptoms and those with other, more obvious intellectual disabilities.

So, what changed? In 2013, the APA did.

“All of these conditions now fall under the umbrella of autism spectrum disorder,” Dr. Cuffman explains. The diagnostic criteria for ASD being more expansive means fewer children fall through the cracks.

It also means the number of people who qualified as being autistic grew overnight.

Genetics

Most of the increase in ASD cases can be explained by the changes in the diagnosis and growing public awareness. But Dr. Cuffman and other researchers concede that there might be some real-world increase. And genetics might be one reason why.

Unlike conditions like Down syndrome, which are the result of a single, specific genetic difference, there are more than 1,000 potential genetic changes that can result in ASD.

Autism can also be hereditary. More autistic people than ever before are getting support at a young age. Those early interventions are improving quality of life and making it easier for autistic people to have relationships — and children — as adults. As their children are more likely to be autistic, it’s also likely that the population will continue to rise.

Environmental exposure

“Events that impact the health of a fetus or newborn are big risk factors for autism,” Dr. Cuffman notes. Here are a few examples:

• Issues with oxygenation (the fetus not getting enough air)
• The mother having an infection
• Exposure to toxic substances like alcohol, opioids or lead
• Interacting with polluted air, water or soil

Some of these fetal health hazards — like opioid exposure — have become more common. That may play a role in rising ASD numbers.

Modern medicine

The circumstances of your birth play a role in your likelihood of having autism. ASD is more common when one or more of the following are true about a child:

• Their mother’s age is over 35
• Their father’s age is over 40
• They were born preterm
• The pregnancy had significant complications
• Their birth weight was low

You may be noticing a pattern here: Medical advances mean that children who may not have survived in the past are alive and well today. And it just so happens that those same kids are more likely to have neurodevelopmental disorders.

Don’t blame vaccines

There’s one thing we know for sure isn’t causing the increase in ASD: vaccines.

In 1998, a doctor and anti-vaccination activist named Andrew Wakefield published a now-discredited paper in The Lancet. In it, he claimed the MMR vaccine caused autism.

The paper was fraudulent. Wakefield manipulated his research findings for financial gain. The Lancet retracted the paper, and Wakefield lost his medical license.

“The Wakefield study was a total lie, but it made its way into the public eye,” Dr. Cuffman laments. It’s one of several misconceptions about the growing prevalence of autism.

Final thoughts

Autism has become more common over recent decades for many reasons. But that doesn’t mean the number we have today is accurate.

The CDC determines autism prevalence by looking at the school and medical records of all the children living in a certain area. They then compare those numbers with data from other areas. That method:

• Misses children who don’t have school or medical records
• Doesn’t control for social determinants of health

For example, the raw data suggests autism rates vary significantly by state. What those numbers actually reveal is the fact that some states likely undercount (and underserve) their autistic population.

So, ASD is probably more common than the 1 in 31 statistic we’re working with right now. As awareness goes up — and support services become more accessible — we should expect the numbers to continue climbing. And that’s a good thing because it means more people are getting the care they deserve.