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How did the prevalence of autism spectrum disorders change before and during COVID-19?

In the recent Centers for Disease Control and Prevention’s Morbidity and Mortality Weekly Report (MMWR), researchers from the United States (US) reported on autism spectrum disorders (ASD) prevalence among four-year-old children in 2020.

Study: Early Identification of Autism Spectrum Disorder Among Children Aged 4 Years — Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, 2020 Image Credit: atsaniuk /


ASD refers to a developmental-type disability that is characterized by communication and/or social interaction deficits, repetitive behavior, and restricted interests. The autism and developmental disabilities monitoring (ADDM) network performs active surveillance to assess the prevalence, characteristics, and timing of autism spectrum disorders among four to eight-year-olds.

About the report

In the present report, researchers reported on ASD prevalence among four-year-olds, compared to the prevalence rates among eight-year-olds, before and during the coronavirus disease 2019 (COVID-19) pandemic in 2020.

In 2020, ASD surveillance was conducted at 11 sites (Arkansas, Arizona, Georgia, California, Minnesota, Maryland, New Jersey, Missouri, Utah, Tennessee, Wisconsin, and Utah) among four to eight-year-old pediatric ASD patients and four-year-olds with clinical suspicion of ASD.

Children in the ASD group had received either (i) ASD diagnosis in the assessments, (ii) special type of education (eligibility) categorization of autism, or (iii) international classification of diseases-ninth revision (ICD-9) or ICD-10 codes.

The team excluded children receiving ICD codes for Rett syndrome without any other ASD indicators. Four-year-olds were suspected of ASD in cases of unmet ASD case definition, but positive statements documented by healthcare professionals indicated ASD.

Data were obtained from education and health records, from the individuals with disabilities education act (IDEA)-part C early intervention (Wisconsin, Utah, and Maryland), Medicaid, and other services that received funding from the state (Wisconsin, California, and Arizona), and disability service programs.

Data on the four-year-old US population residing at the surveillance sites were obtained from the US Census vintage 2021 single-year-of-age and county-level postcensal estimates for 2020. The team adjusted population-level estimates using public school enrollment counts for school districts within the surveillance sites. In cases that missed ethnicity, sex, or race data, information from birth certificates was used.


In 2020, the prevalence of ASD among four-year-olds varied in the included US sites, ranging between 13.0 among every 1,000 pediatric individuals (Utah) and 46.0 among every 1,000 pediatric individuals (California). Overall ASD prevalence was 22 among every 1,000 pediatric individuals and was greater among male children.

In comparison to non-Hispanic Whites, the prevalence of ASD was greater for Hispanics, 1.6-fold greater for non-Hispanic Blacks, 1.8-fold greater for Pacific Islanders, and Asians 1.4-fold. ASD prevalence was greater among children of multiple ethnicities by 1.2-fold. Among 58% of aged four ASD patients with intellectual ability data, 49% had IQ scores of ≤70.

Across all sites, the four-year-olds had a greater cumulative ASD incidence than eight-year-olds, with risk ratios (RR) ranging between 1.3 (among New Jerseyans and Utahans) and 2.0 (among Tennesseans).

Among the pediatric individuals with documented developmental assessments, 78% were assessed by three years of age. The rates varied between 67% (Tennessee) and 88% (Arkansas) and were lower among Blacks than Hispanics.

Six months before the World Health Organization (WHO)’s severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic announcement in March 2020, 1,593 more assessments and 1.90 more ASD cases were identified among every 1,000 pediatric individuals aged four years compared to statistics four years prior (when the eight-year-olds were identified).

Post-six months of COVID-19 onset, the patterns reversed with 217 lesser assessments and 0.3 lesser cases identified among every 1,000 pediatric individuals four years of age compared to four years prior.

The patterns did not recover to pre-pandemic rates through end-2020 across sites. For 2020, suspected ASD prevalence rates ranging between 0.5 in California and 10 in Arkansas among every 1,000 pediatric individuals of four years were observed. These were greater than in 2018 for Arkansas, Arizona, New Jersey, Utah, and Maryland. Similar cognitive and demographic characteristics were observed for the four-year-olds with ASD or suspected ASD.


Based on the report findings, ASD prevalence among four-year-olds varied across sites, indicating differences in the early autism spectrum disorder detection practices in community settings. In 2020, across sites, the cumulative ASD incidence at four years of age was greater than among eight-year-olds, indicative of improvements in the earlier ASD identification.

Persistently fewer ASD evaluations and case identifications post-COVID-19 onset indicate healthcare evaluation disruptions associated with the SARS-CoV-2 outbreak through 2020.

Sites showing greater recovery could mitigate care disruptions more effectively, e.g., switching to tele-based practices for ASD evaluations. Further research assessing the impact of COVID-19-associated disruptions in ASD identification and evaluation could aid in developing mitigation strategies to prevent disruptions. In turn, this could result in better practice during future pandemics and other population health emergencies. Earlier ASD identification could influence disease management and improve outcomes.

Journal reference:
  • Shaw KA, Bilder DA, McArthur D, et al. Early Identification of Autism Spectrum Disorder Among Children Aged 4 Years — Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, 2020. MMWR Surveill Summ 2023;72(No. SS-1):1–15. DOI:,

Posted in: Child Health News | Medical Research News | Medical Condition News | Disease/Infection News

Tags: Autism, Children, Coronavirus, Coronavirus Disease COVID-19, covid-19, Disability, Education, Healthcare, International Classification of Diseases, Medicaid, Mortality, Pandemic, Research, Respiratory, Rett Syndrome, SARS, SARS-CoV-2, Severe Acute Respiratory, Severe Acute Respiratory Syndrome, Syndrome

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Pooja Toshniwal Paharia

Dr. based clinical-radiological diagnosis and management of oral lesions and conditions and associated maxillofacial disorders.

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