Autism rates surge in California, with steepest rise among minority children in lower-income counties

• A new study published in Sage Open Medicine found autism diagnoses accelerated sharply among California children born in 2016, with a “changepoint” marking dramatically higher rates.
• The steepest increases occurred among Black and Hispanic children in lower- and middle-income counties, with Black children in Los Angeles County approaching 9.5% prevalence.
• California’s Department of Developmental Services data shows an estimated 3.9% autism rate for children born in 2019, up from 1.5% for those born in 2013.
• Researchers identified the 2016 changepoint as coinciding with California Senate Bill 277, which eliminated personal belief exemptions for school vaccinations.
• CDC data confirms California leads the nation in autism prevalence, with 5.31% of 8-year-olds born in 2014 diagnosed, while national rates continue climbing without clear explanation.

New data reveals accelerating autism diagnoses and widening disparities across California

California’s autism rates have surged dramatically among children born in the mid-2010s, with the steepest increases concentrated among Black and Hispanic children in lower-income counties, according to a new study published Sept. 24 in Sage Open Medicine. Researchers analyzing two decades of California Department of Developmental Services data identified a striking “changepoint” in 2016, when autism diagnoses began climbing much more rapidly and unevenly across racial and socioeconomic lines. The findings raise urgent questions about the drivers of what researchers called “a pressing public health concern” as rates approach unprecedented levels.

The changepoint: 2016

Researchers Cynthia Nevison of Rutgers University and Walter Zahorodny examined autism cases recorded between 1993 and 2020 across California’s 36 most populous counties, breaking down data by Asian, Hispanic, Black and white populations. They found autism prevalence surged statewide over the past decade, but a clear acceleration began with children born in 2016.

For children born between 2000 and 2014, autism rates in lower-income counties had been rising among both white and Hispanic children. After 2015, that rate accelerated sharply. By 2020, autism prevalence reached an estimated 8.7% for white children in lower-income Butte County and 4.9% for Hispanic children in Fresno and Tulare counties.

The timing of the changepoint is notable. California Senate Bill 277 took effect Jan. 1, 2016, eliminating personal belief and religious exemptions for school and childcare immunization requirements. Children’s Health Defense Chief Scientific Officer Brian Hooker said that corresponds directly to the changepoint identified in the study.

Racial disparities widen dramatically

Black children experienced consistently higher autism prevalence than white, Asian and Hispanic children across the nine counties with sufficient data for analysis. Among Black children in Los Angeles County born in 2019, the autism rate approached 9.5%. It reached roughly 8% in Sacramento, Fresno and Kern counties, and approximately 6-7% in Orange and San Diego counties.

Statewide, DDS data shows for children born in 2019, autism rates were highest among Black children at 6.0%, followed by Hispanic children at 3.4%, Asian children at 3.0% and white children at 2.7%. The race and ethnicity disparities widened for the youngest children studied.

The data supports anecdotal evidence from California teachers who report worsening situations in autism learning centers in public schools, according to Nevison. Teachers report more students exhibiting challenging behaviors, teacher burnout and resulting staffing issues.

California leads nation, but undercounts may mask true scope

California consistently records the highest autism rates among all U.S. locations tracked by the CDC’s Autism and Developmental Disabilities Monitoring Network. In the most recent ADDM report, California reported autism rates of 5.31% in 8-year-olds born in 2014, and 6.06% in 4-year-olds born in 2018.

However, the new study suggests California’s DDS data may identify only about half of all autism cases, significantly underestimating the true scope. The ADDM network, which tracks autism rates at 16 sites nationwide, found a mean ASD prevalence of 3.2% among 8-year-olds born in 2014 nationally. Maryland recorded the lowest rates at 2.3%, while California led at 4.5%.

Walter Zahorodny, coauthor of the Rutgers study and director of the New Jersey Autism Study, noted that California’s figures are drawn from areas with aggressive screening programs that may produce more accurate counts than other states. “The true rate may not be substantially different between California and other ADDM states,” he said previously. “What’s different is that California implemented some wide-ranging screening and intervention programs.”

Questions linger on what drives the rise

Researchers increasingly agree that autism results from a complex interaction of genetic factors and early environmental insults, including neuroinflammation, immune dysregulation and oxidative stress during critical stages of neurodevelopment. Yet the specific causes driving the continued increase remain unclear.

The CDC’s most recent reports did not delve into reasons behind the continued rise. CDC epidemiologist Kelly Shaw suggested increased access to evaluations and diagnoses might explain some of the increase but acknowledged that explanation is incomplete.

Two multi-million dollar studies in California found that better awareness, changes in diagnostic criteria and earlier age of diagnosis explained only a small fraction of the rise. Those researchers called for greater emphasis on investigating potential toxicants that might be driving the increase.

The recent California study did not address possible causes but concluded that “understanding the factors driving diagnosed ASD prevalence up to the high levels reported in this study is a pressing public health concern.”

A growing challenge with no end in sight

The data shows no sign of autism rates leveling off, with the most severe increases occurring among populations least able to access supportive resources. As Nevison noted, “ASD prevalence is growing and increasingly the students who are most severely affected are those whose families are least able to cope or afford nutritious food and other health-promoting therapies.”

Once considered a rare disorder, autism now affects such a significant portion of children that researchers question whether the health care and educational infrastructure can keep pace. The question of what is driving the increase remains unanswered, but the evidence is clear: the rates are climbing faster than ever, and the burden is falling heaviest on communities with the fewest resources.

Sources for this article include:

ChildrensHealthDefense.org

SagePub.com

RutgersHealth.org