Last updated on November 26, 2023
The United States Centers for Disease Control and Prevention released a data analysis on December 3, 2021, suggesting 1 in 44 children are categorized as autistic by age eight in the United States.
Is the 2.3 percent rate accurate nationally, using current diagnostic instruments? These data present a curious question: Why do state diagnostic rates vary widely? Missouri data indicate a diagnostic rate of 1.5 to 1.8 percent, while California data indicate an autism diagnostic rate of 3.9 to 4.2 percent, roughly double the diagnostic rate in Missouri.
We need to understand why state diagnostic rates vary, but those are complicated research questions.
The demographic data on intelligence measures suggest one explanation, which merits further study. California and Minnesota were far more likely than other states to have children diagnosed as autistic with IQ scores greater than 85. In those two states, half of the autistic children had IQs greater than 85. By comparison, more than half the identified autistic children in Tennessee had IQ scores at or below 70 on standard test instruments.
It also remains true that males receive the diagnostic label autistic four times more frequently than females, across all states regardless of the overall diagnostic rates. There are some conditions that have gender or ethnic correlations, but is autism a “male” diagnosis or are mental health professionals missing most female autistics? My assumption is that we’re missing many of the female autistics, but science isn’t based on assumptions.
Discussion of autism will now focus on the “rising prevalence,” which is likely explained by greater screening capabilities and broader diagnostic criteria for autism in the DSM5.
Media outlets embraced the 2.3 percent story, with its convenient “1 in 44” headline.
- Axios: CDC: Data suggests 1 in 44 children diagnosed with autism
- Los Angeles Times: New data suggests 1 in 44 US children affected by autism
- DisabilityScoop: CDC Says 1 In 44 Kids Have Autism
The full CDC report is part of its ongoing survey of medical diagnostic data. The data analyzed represent 2018 reporting to the agency.
Prevalence and Characteristics of Autism Spectrum Disorder Among Children Aged 8 Years — Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, 2018
Surveillance Summaries / December 3, 2021 / 70(11);1–16Abstract
Problem/Condition: Autism spectrum disorder (ASD).Period Covered: 2018.
Description of System: The Autism and Developmental Disabilities Monitoring (ADDM) Network conducts active surveillance of ASD. This report focuses on the prevalence and characteristics of ASD among children aged 8 years in 2018 whose parents or guardians lived in 11 ADDM Network sites in the United States (Arizona, Arkansas, California, Georgia, Maryland, Minnesota, Missouri, New Jersey, Tennessee, Utah, and Wisconsin). To ascertain ASD among children aged 8 years, ADDM Network staff review and abstract developmental evaluations and records from community medical and educational service providers. In 2018, children met the case definition if their records documented 1) an ASD diagnostic statement in an evaluation (diagnosis), 2) a special education classification of ASD (eligibility), or 3) an ASD International Classification of Diseases (ICD) code.
Results: For 2018, across all 11 ADDM sites, ASD prevalence per 1,000 children aged 8 years ranged from 16.5 in Missouri to 38.9 in California. The overall ASD prevalence was 23.0 per 1,000 (one in 44) children aged 8 years, and ASD was 4.2 times as prevalent among boys as among girls. Overall ASD prevalence was similar across racial and ethnic groups, except American Indian/Alaska Native children had higher ASD prevalence than non-Hispanic White (White) children (29.0 versus 21.2 per 1,000 children aged 8 years). At multiple sites, Hispanic children had lower ASD prevalence than White children (Arizona, Arkansas, Georgia, and Utah), and non-Hispanic Black (Black) children (Georgia and Minnesota). The associations between ASD prevalence and neighborhood-level median household income varied by site. Among the 5,058 children who met the ASD case definition, 75.8% had a diagnostic statement of ASD in an evaluation, 18.8% had an ASD special education classification or eligibility and no ASD diagnostic statement, and 5.4% had an ASD ICD code only. ASD prevalence per 1,000 children aged 8 years that was based exclusively on documented ASD diagnostic statements was 17.4 overall (range: 11.2 in Maryland to 29.9 in California). The median age of earliest known ASD diagnosis ranged from 36 months in California to 63 months in Minnesota.
Among the 3,007 children with ASD and data on cognitive ability, 35.2% were classified as having an intelligence quotient (IQ) score ≤70. The percentages of children with ASD with IQ scores ≤70 were 49.8%, 33.1%, and 29.7% among Black, Hispanic, and White children, respectively. Overall, children with ASD and IQ scores ≤70 had earlier median ages of ASD diagnosis than children with ASD and IQ scores >70 (44 versus 53 months).
Interpretation: In 2018, one in 44 children aged 8 years was estimated to have ASD, and prevalence and median age of identification varied widely across sites. Whereas overall ASD prevalence was similar by race and ethnicity, at certain sites Hispanic children were less likely to be identified as having ASD than White or Black children. The higher proportion of Black children compared with White and Hispanic children classified as having intellectual disability was consistent with previous findings.
From the study text, I have replicated Tables 2 and 5 to offer readers the opportunity to compare data by state, gender, and cognitive measures.
Autism Prevalence Rates
What we see in Table 2 are indications that gender and diagnostic practices must be studied further. As a parent of two young girls, I know that schools and mental health professionals are slow — even resistant — to diagnose girls as autistic or with attention deficit. Instead, professionals quickly mention depression and mood disorders instead of sensory processing, executive function, and other neurodiverse indicators.
Again, we also see the state-by-state diagnostic rate variations in Table 2.
| Site | Overall | Male prevalence (95% CI) |
Female prevalence (95% CI) |
Male-to-female prevalence ratio (95% CI) |
||
|---|---|---|---|---|---|---|
| No. with ASD | Total population | Prevalence (95% CI) |
||||
| Arizona | 331 | 13,313 | 24.9 (22.4–27.6) |
37.9 (33.6–42.7) | 11.2 (8.9–14.1) | 3.4 (2.6–4.4) |
| Arkansas | 353 | 15,435 | 22.9 (20.6–25.3) |
36.7 (32.8–41.1) | 8.1 (6.3–10.4) | 4.5 (3.4–5.9) |
| California | 586 | 15,076 | 38.9 (35.9–42.1) |
64.4 (59.2–70.2) | 12.3 (10.0–15.1) | 5.2 (4.2–6.5) |
| Georgia | 514 | 23,580 | 21.8 (20.0–23.7) |
35.2 (32.1–38.7) | 7.8 (6.3– 9.5) | 4.5 (3.6–5.7) |
| Maryland | 423 | 20,666 | 20.5 (18.6–22.5) |
33.1 (29.8–36.7) | 7.5 (6.0– 9.3) | 4.4 (3.5–5.7) |
| Minnesota | 277 | 10,081 | 27.5 (24.5–30.9) |
43.7 (38.5–49.7) | 10.4 (7.9–13.6) | 4.2 (3.1–5.7) |
| Missouri | 405 | 24,481 | 16.5 (15.0–18.2) |
25.0 (22.4–27.9) | 7.6 (6.2– 9.4) | 3.3 (2.6–4.1) |
| New Jersey | 491 | 17,289 | 28.4 (26.0–31.0) |
45.6 (41.4–50.1) | 10.1 (8.2–12.5) | 4.5 (3.6–5.7) |
| Tennessee | 573 | 25,237 | 22.7 (20.9–24.6) |
36.0 (32.9–39.3) | 8.8 (7.3–10.6) | 4.1 (3.3–5.1) |
| Utah | 548 | 25,459 | 21.5 (19.8–23.4) |
33.1 (30.2–36.3) | 9.3 (7.7–11.1) | 3.6 (2.9–4.4) |
| Wisconsin | 557 | 29,664 | 18.8 (17.3–20.4) |
30.0 (27.4–32.8) | 7.1 (5.9– 8.6) | 4.2 (3.4–5.2) |
| Total | 5,058 | 220,281 | 23.0 (22.3–23.6) |
36.5 (35.4–37.6) | 8.8 (8.2– 9.4) | 4.2 (3.9–4.5) |
Autism and Cognitive Instrument Scores
There remains a heated debated within the autism communities regard the DSM-IV-TR and DSM5 criteria for autism diagnoses. Before the DSM-IV, autism was generally a label applied only when cognitive impairment was comorbid with autistic traits. The mental health professionals, instrument designers, and DSM committees delineated between classic autism and PDD-NOS (Pervasive Developmental Disorder, Not Otherwise Specified).
Should the “spectrum” model adopted in the DSM5 be revisited to once again delineate cognitive disabilities? I find reasonable arguments for and against. The CDC data suggest cognitive instrument scores do influence diagnosticians differently in various regions of the United States.
| Site/Characteristic | Total no. with ASD | With IQ information | Cognitive level | ||
|---|---|---|---|---|---|
| No. (%) | IQ ≤70 (%) | IQ = 71–85 (%) | IQ >85 (%) | ||
| Site | |||||
| Arizona | 331 | 290 (87.6) | 31.4 | 23.8 | 44.8 |
| Arkansas | 353 | 313 (88.7) | 39.9 | 25.2 | 34.8 |
| California | 586 | 454 (77.5) | 20.5 | 25.6 | 54.0 |
| Georgia | 514 | 353 (68.7) | 38.5 | 18.4 | 43.1 |
| Maryland | 423 | 141 (33.3) | 44.7 | 17.7 | 37.6 |
| Minnesota | 277 | 225 (81.2) | 28.9 | 19.1 | 52.0 |
| Missouri | 405 | 130 (32.1) | 26.2 | 24.6 | 49.2 |
| New Jersey | 491 | 315 (64.2) | 34.6 | 27.3 | 38.1 |
| Tennessee | 573 | 360 (62.8) | 52.5 | 19.2 | 28.3 |
| Utah | 548 | 207 (37.8) | 27.1 | 31.9 | 41.1 |
| Wisconsin | 557 | 219 (39.3) | 44.7 | 20.5 | 34.7 |
| Total | 5,058 | 3,007 (59.5) | 35.2 | 23.1 | 41.7 |
| Sex | |||||
| Female | 945 | 537 (56.8) | 35.6 | 25.3 | 39.1 |
| Male | 4,111 | 2,470 (60.1) | 35.1 | 22.6 | 42.2 |
| Race/Ethnicity | |||||
| White, non-Hispanic | 2,407 | 1,402 (58.2) | 29.7 | 22.7 | 47.6 |
| Black, non-Hispanic | 1,041 | 570 (54.8) | 49.8 | 21.9 | 28.2 |
| Hispanic | 1,019 | 677 (66.4) | 33.1 | 25.7 | 41.2 |
Concluding Thoughts
Labels change. Autism rates have increased while other diagnoses have fallen. This trend is clear in the Office of Special Education Programs data. Even with the overall percentage of students receiving services is stable, the breakdown of labels shifts with the DSM and the training of diagnosticians.
If autistic are 4 percent of the population, then we’re not divergent. We’re not all that unusual, statistically. In fact, many “normal” traits would be rarer. If diagnostic criteria nationally come to reflect the practices of professionals in California and Minnesota, I expect autism to have a five percent incidence rate, leading to the headline “One in Twenty Children Now Diagnosed Autistic!”
Just wait until more young women are properly diagnosed. That could double the reported autism incidence rates.
At a 1-in-20 rate, I suspect autism criteria will be revised by the American Psychiatric Association, with a future DSM edition limiting “autism” while expanding or creating another diagnostic label.
Autism is not increasing, many of us theorize. The diagnostic practices are changing.