Weekend Reads | The Rise of Autism Spectrum Disorder Diagnoses

In 1966, it was estimated that 1 in 2,500 people had autism (now referred to as autism spectrum disorder, or ASD). By 1987, it was 1 in 1,400; in 2000, 1 in 150; in 2008, 1 in 88. By 2017, the figure was 1 in 68, and in a new report (this weekend’s read), for children age 8 or younger in the U.S., it’s now about 1 in 33 (or 3%). Trying to understand the reasons for the dramatic increase in autism diagnoses over the past 60 years is a topic of great discussion and consternation among health professionals.

The new report breaks out ASD diagnosis rates at 12 sites across the country that are part of the Mental Health Research Network and funded by the National Institute of Mental Health and the Centers for Disease Control and Prevention (CDC) to collect data on ASD diagnosis (among many other things). The data shows a steady rise in diagnoses between 2011 and 2022.

There are two prevailing hypotheses for the increase. The first is that there are actually more people with ASD today than there were in the past. The second is that more people are receiving ASD diagnoses today because of higher awareness of ASD and changes in diagnosis and screening practices. There is a decent argument for each, and they are not mutually exclusive, so it’s entirely possible both are true.

While we don’t know exactly what mechanism causes ASD, researchers have confirmed that there is a strong genetic component to it; according to a 2017 study, 83% is genetic and 17% is environmental. They have also identified about 100 locations in our DNA that consistently correlate with ASD. There are also some other contributing factors to a possible increase in the prevalence of ASD; for example, having older biological parents (particularly an older father) leads to increased risk of ASD, and we know that in recent decades, many couples have chosen to delay having kids. Also, premature infants have a higher risk for ASD, and improvements in health care over recent decades has led to more premature infants surviving. All of this suggests there may truly be more people with ASD today than in the past.

But there is also a strong case to be made that there are far more people being screened for ASD than in the past, and the screening/diagnosis criteria have broadened such that a larger percentage of the people screened would now be assessed as having ASD. In 2006, the American Academy of Pediatrics issued a new recommendation that all children should be screened for ASD at their regular checkups at 18 and 24 months. The data shows that by far the largest increase in diagnosis rates is for children 8 and younger, when autism symptoms typically first appear and when children are likely to get screened. Also, as ASD diagnoses have increased, diagnoses of mental disability have decreased; that suggests that many people were misdiagnosed in the past.

The new report also highlights some trends suggesting that ASD screening and diagnosis has suffered from gender and racial/ethnic biases, which over time are being overcome as the process becomes more widespread and consistent. 

It’s long been true that more boys than girls are diagnosed with ASD, but the gap has narrowed; while in 2011, for children it was 4.3 boys to every 1 girl, by 2022, the ratio had declined to 3.01 to 1. This is mainly because the diagnosis rate for girls has increased faster than for boys.

Historically, autism was also considered to be most prevalent among white people, but the latest data shows this is no longer the case. Among children, the highest rate of ASD diagnosis is now among American Indian/Alaska Native people, with the second-highest rate for Black people. Hispanic children also now have a higher diagnosis rate than non-Hispanic children, a dramatic reversal from 2011.

One last data point suggests that changes in the screening process may be a large factor: For one year, 2020, the diagnosis rate was flat. That, of course, was the first year of the COVID-19 pandemic, when many routine health care procedures, including checkups, were disrupted, and lots of kids attended school from home. In 2021, the numbers started going back up again.

The report doesn’t try to give a definitive answer to why the rate is going up; in fact, it begs off trying to give an answer at all. But it does draw one conclusion from the data that should be of concern: We are looking at a tsunami wave of people with ASD diagnoses working their way into adulthood. Depending on where they are on the spectrum, some will be able to function and thrive independently in adult society. But many will need assistance of various forms, and at the moment, we do not have the infrastructure or services available to support them and provide for their needs. Many programs and services have been built out to support children with ASD, but far fewer exist for adults. As the authors say, “This population faces significant challenges to address health care needs, also referred to as the ‘services cliff,’ in part due to lack of comprehensive or integrated services and accommodations in adult care. Continuity of care is especially important considering autistic young adults experience elevated rates of diabetes, obesity, anxiety, depression, and other conditions.”

This kind of generational change happens in health care — and in society. Over the 20th century, we saw the expected lifetime of a person in the U.S. extend significantly, which meant we needed to create infrastructure to support a lot more elderly people (with all of the health issues that accompany old age). We have yet to discover if there are long-term health complications for people who contracted COVID-19, particularly those who became very sick. We also need to wrestle with the long-term health effects of drug addiction (or former drug addiction) for a large number of people. And add to that this new challenge: an increasing population of people diagnosed with ASD who want to live happy, thriving adult lives into their golden years. 

Autism Diagnosis Among US Children and Adults, 2011-2022