Autism spectrum disorder has grown 10% since 2014


Researchers at the Johns Hopkins Bloomberg School of Public Health contributed to a new U.S. Centers for Disease Control and Prevention report that finds the prevalence of autism spectrum disorder (ASD) among 11 surveillance sites as 1 in 54 among children aged 8 years in 2016 (or 1.85 percent).

This is a 10 percent increase from the most recent report two years ago when it was 1 in 59, and the highest prevalence since the CDC began tracking ASD in 2000. Consistent with previous reports, boys were 4 to 5 times more likely to be identified with ASD than girls.

The rate for ASD is 1 in 34 among boys (or 2.97 percent) and 1 in 145 among girls (or 0.69 percent).

ASD is a developmental disorder characterized by social and communication impairments, along with limited interests and repetitive behaviors. Early diagnosis and intervention are key to improving learning, communication, and other skills.

Rates have been rising dramatically in the past three decades, but researchers do not know how much of this rise is due to better detection or an increase in “true” cases or both. Technical factors that may be contributing to an increase in ASD include increased awareness, screening, diagnostic services, treatment and intervention services, better documentation of ASD behaviors, and changes in diagnostic criteria.

To date, the causes of autism are not completely understood but studies show that both environment and genetics may play a role.

As in its prior report, the CDC collected data at 11 regional monitoring sites across the U.S. that are part of the Autism and Developmental Disabilities Monitoring (ADDM) Network.

The ADDM Network makes its estimates in the participating communities by reviewing health and/or education records to ensure as complete a count as possible. ADDM does not rely solely on the presence of a documented ASD diagnosis; it also counts ASD cases determined by ADDM expert clinicians who review the records.

The Maryland-ADDM monitoring site is based at the Johns Hopkins Bloomberg School of Public Health.

This is the seventh report by the ADDM Network, which has used the same surveillance methods each time. Estimated prevalence rates of ASD in the U.S. reported by previous data were:

  • one in 59 children in the 2018 report based on 2014 data
  • one in 68 children in the 2016 report based on 2012 data
  • one in 68 children in the 2014 report based on 2010 data
  • one in 88 children in the 2012 report based on 2008 data
  • one in 110 children in the 2009 report based on 2006 data
  • one in 150 children in the 2007 report based on 2000 and 2002 data

“We need to know how many children have ASD in order to prepare our communities and services systems,” says Li-Ching Lee, PhD, ScM, a psychiatric epidemiologist with the Bloomberg School’s departments of Epidemiology and Mental Health and the principal investigator for Maryland-ADDM.

“An ongoing and accurate estimate will help to develop realistic plans to support these children now, and later into their adolescence and adulthood.”

For the first time in ADDM’s history, researchers found no statistically significant difference in the ASD prevalence between black and white children. This may suggest progress toward earlier and more equitable identification of ASD, the researchers say.

“Although the gap related to the prevalence of racial and ethnic differences is closing, disparities in early intervention persist for racial and ethnic minorities,” Lee said. “Black and Hispanic children with ASD were evaluated at older ages and were more likely to have intellectual disability than white children.” Later diagnosis can hinder early intervention, considered the most effective treatment for ASD.

In Maryland, the prevalence of ASD was 1 in 52 children: 1 in 33 for boys and 1 in 128 for girls. The data were derived from health and special education records of children who were 8 years old and living in Baltimore County in 2016.

For the first time in ADDM’s history, researchers found no statistically significant difference in the ASD prevalence between black and white children.

ASD can be diagnosed as early as 24 months of age.

In Maryland, however, only 48.3 percent of children with ASD received a comprehensive evaluation by 36 months, and the median age at earliest ASD diagnosis was 48 months.

“This lag may delay the timing for children with ASD to get diagnosed and receive needed services,” says Lee, who is an associate director of the school’s Wendy Klag Center for Autism and Developmental Disabilities.

The CDC recommends that parents track their child’s development, act quickly, and get their child screened if they have a concern. Free checklists and information for parents, physicians, and child care providers are available at

A full copy of the report, “Prevalence of Autism Spectrum Disorder Among Children Aged 8 Years–Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, 2016” is available on the CDC website:

A copy of the Community Report with individual state statistics is available:


Autism Spectrum Disorders (ASD) comprise a range of pervasive neurodevelopmental disorders with a population prevalence of approximately 1%1. They are characterized by early-onset persistent impairments in social communication and interaction as well as the presence of restricted, repetitive behaviors or interests2,3.

Diagnosing ASD is a complicated, lengthy and time-consuming process, which requires outstanding and specific clinical expertise4,5. Although research makes constant progress in understanding the underlying genetic and neurobiological factors associated with ASD, there are currently no reliable biological markers for ASD and the diagnosis remains based on behavioral symptoms1,6,7.

The current so-called “gold standard” of ASD diagnosis comprises the use of various standardized diagnostic instruments that assist clinicians in reaching a best-estimate clinical diagnosis79. Two of the most widely used diagnostic instruments are the Autism Diagnostic Observation Schedule (ADOS respectively ADOS-2 for the revised second edition)10,11 and the Autism Diagnostic Interview – Revised (ADI-R)12.

The ADI-R is a semi-structured interview administered to parents or caregivers that focuses on developmental history and current symptom presentation.

The ADOS is a standardized semi-structured diagnostic observation scale designed to assess important social-communicative behaviors as well as stereotypic and repetitive behavioral features.

The ADOS includes four different modules for different age and language levels, with Module 4 intended for verbally fluent adolescents and adults. For each module, there is a diagnostic algorithm that allows for the classification of ASD or non-ASD10,11,13,14.

The ADOS is one of the psychometrically best-evaluated diagnostic tools in ASD, especially in children (Modules 1 and 2)4,1517, with fewer studies investigating the ADOS in adolescents and adults (Modules 3 and 4)1821.

Although a good psychometric quality has been widely demonstrated, existing studies suggest a lower diagnostic utility in naturalistic clinical settings as well as with older individuals8,2224.

While most cases with ASD are diagnosed in childhood, the diagnosis oftentimes remains unnoticed until adolescence and adulthood, particularly in those individuals with at least average cognitive and language abilities, better adaptive functions and more subtle symptom presentations25,26.

Diagnosing ASD in high-functioning adolescents and adults (i.e. without intellectual disability) can be even more challenging compared to childhood due to various factors: a care-giver based developmental history as acquired with the ADI-R is oftentimes unavailable in older individuals25 and the individual’s self-report of symptoms may be diminished due to impaired self-referential cognition27.

Additionally, learned compensatory skills might conceal impairments, thereby reducing diagnostic accuracy of observational tools such as the ADOS25.

Furthermore, most adults with ASD have at least one comorbid psychiatric disorder1,28 and ASD symptoms frequently overlap with those of other psychiatric conditions19,23 thereby further complicating differential diagnosis.

Nonetheless, establishing an accurate and timely diagnosis is of great importance for those affected and the planning of suitable psychosocial interventions in order to promote positive outcome2931.

Previous studies have applied machine learning techniques to examine whether the process of diagnosing ASD can be improved by statistically identifying reduced subsets of features from existing diagnostic instruments reaching from self-administered screening questionnaires to clinician-administered diagnostic tools (for a recent overview, see Thabtah32).

A few authors have shown that efficiency and accessibility of existing pre-diagnostic screening questionnaires such as the Autism-Spectrum Quotient (AQ)3335 or the Social Responsiveness Scale (SRS)36,37 can be improved using machine learning. Similar machine learning experiments have been run to identify subsets of behavioral features from clinician-administered diagnostic tools, namely ADOS (Module 1 to 3)3842 and ADI-R36,39,43.

Findings of these studies suggest that ASD detection in children can be achieved with substantially fewer items compared to the original ADOS and ADI-R algorithms while retaining high diagnostic accuracy, sensitivity and specificity. To our knowledge, this has not yet been examined in a sample of adolescents and adults as assessed with the ADOS Module 4.

The purpose of the present study therefore was to expand on the existing literature with a specific focus on high-functioning adolescents and adults. Advances of the present study are a large and balanced routine clinical sample of adolescents and adults with best-estimate clinical diagnoses of ASD and relevant psychiatric differential diagnoses, thereby being a good representation of the actual population presenting to ASD assessment settings. We aim to identify the diagnostically most informative features from the ADOS Module 4 that accurately differentiate between individuals with ASD and individuals with other clinically complex presentations using a data-driven machine learning approach.

Although all items of the ADOS focus on relevant behavioral concepts, some items may be more discriminative and have higher classification ability particularly in a challenging clinical sample of older individuals that were all initially suspected of ASD.

Identifying essential subsets of behavioral features that distinguish ASD from non-ASD cases could contribute to an enhancement of the complex diagnostic process in multiple ways: to improve existing diagnostic tools (i.e. revise existing classification algorithms), to shorten existing diagnostic tools such as the ADOS (for a critical discussion, however, see Bone and colleagues36) and/or to inform the development of novel diagnostic tools and methods for initial screening based on these essential constructs.

How is ADOS (Autism Diagnostic Observation Schedule) Used to Identify ASD?

ADOS stands for Autism Diagnostic Observation Schedule. ADOS is a standardized diagnostic test for Autism Spectrum Disorder (ASD), published by Western Psychological Services (WPS) in 2000 and now available in 15 different languages. Since that time, it has become one of the standard diagnostic tools both school systems and independent clinicians use when screening for developmental disabilities.

ADOS is not required to make a diagnosis of autism. The current edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) governs the criteria for making an autism spectrum diagnosis, which any psychologist or psychiatrist can do using whatever methods they find effective.

What ADOS does is provide a systematic and standardized method for identifying kids with ASD. The process involves making direct observations under controlled circumstances that other clinicians are able to replicate.

Only trained professionals can administer the ADOS diagnostic screening, but it eliminates some of the differences of opinion otherwise possible when two different experts provide a diagnosis without following common guidelines.

Although it’s not the only standardized diagnostic exam for ASD (the other popular option, the Autism Diagnostic Interview-Revised, is also published by WPS), it’s very likely that if you suspect your child may be showing traits that suggest they might be on the spectrum, they will have to go through an ADOS exam at some point. Here’s what you need to know about the process.

What to Expect When Agreeing to Allow Your Child to Be Screened

ADOS consists of four different modules. Each of them is designed to provide the most appropriate test for an individual at a certain age or functional level:

  • Module One – Designed for individuals who do not have consistent verbal communication skills. Uses entirely non-verbal scenarios for scoring.
  • Module Two – Designed for individuals who have minimal verbal communication skills. This may include young children at age-appropriate skill levels; most scenarios require moving around the room and interacting with objects.
  • Module Three – Designed for individuals who are verbally fluent and capable of playing with age-appropriate toys. Can be conducted largely at a desk or table.
  • Module Four – Designed for individuals who are verbally fluent but beyond the age of playing with toys. Incorporates some Module Three elements but also more conversational aspects regarding daily living experiences.

Each module consists of a set of standardized scenarios that the tester walks the subject through. For example, the presenter lays out a picture that provides a template for your child to place blocks on. The child is intentionally not provided enough blocks to fully complete the task, but the tester shows that they have more. How your child handles the dilemma is observed and evaluated. Do they make a polite request for the extra blocks? Point and scream? Refuse to continue? Each reaction is a scorable behavior for the examiner.

Other components include structured conversations or social scenarios, like a pretend birthday party or snack time. In many of them, minor obstacles are intentionally introduced; things like withholding the blocks, to see how the child copes with it.

The examiner will use a hierarchy of structures called presses to cue responses. In general, the child is expected to show initiative in the early parts of the test, without outside prompting; if this does not occur, the examiner will provide more and more specific tasks to make sure they have a behavior to score.

This can make the test difficult to watch, particularly for parents. You naturally want to provide assistance and make things smoother, but the entire point of the test is to see how the child does without your assistance. Many examiners strongly discourage parents from being in the room when their child is tested, both because of the impulse to help and because parents can present a distraction.

Each module takes around 40 minutes to complete, but, because the modules are oriented at different types of subjects with different behavioral and cognitive issues, not all modules are necessarily used. However, the examiner may choose to use another module after finding that the originally selected one didn’t match the functional abilities of the child closely enough for an accurate score.

An ADOS Score is Just One Element of an ASD Diagnosis

Typically, the test will be recorded on video so a team can review it and make the diagnosis. This helps eliminate otherwise subjective biases that are inherent in any individual clinician’s work.

The behaviors of the test subject are given a score of between zero and three, weighed against the normal behavior of a neurotypical person taking the test. Zero indicates a normal behavior while three indicates abnormal function.

The sum of the individual behavior scores is the overall score on the test module. The threshold levels for an ASD diagnosis may vary according to both module and age-level… a 13 on Module 3 might be perfectly normal for an 8-year-old, but indicate low-functioning ASD for a 19-year-old.

It’s common to look for second opinions even after getting an ADOS test score, and it’s important to note that ADOS alone should not be the sole criteria for making a diagnosis—it cannot account for stereotyped behaviors or interests or histories of developmental delays, both key DSM-5 criteria. An ADI-R screening might also be administered as a secondary test to gather more data.

ADOS is constantly being refined and studied to make it more accurate and useful. The test is on its second major revision and further studies are ongoing.

Johns Hopkins Bloomberg School of Public Health


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