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Developmental Disabilities

Tracking Developmental Disabilities

No nation-wide system actively tracks all developmental disabilities. The Environmental Public Health Tracking Network is currently using two developmental disabilities data sources:

  • CDC's Autism and Developmental Disabilities Monitoring (ADDM) Network, and
  • Department of Education's Individuals with Disabilities Education Act (IDEA).

The Tracking Network currently includes data for seven developmental disabilities. Read more about these developmental disabilities. Data on the prevalence of autism spectrum disorders (ASDs) and other developmental disabilities comes from the Autism and Developmental Disabilities Monitoring (ADDM) Network. Data on the number of students receiving special education services under specific disability categories are reported by the Department of Education (ED) as part of the Individuals with Disabilities Education Act (IDEA). These two sources provide different kinds of data. The ADDM Network provides the number of existing cases of ASDs in a defined population. The IDEA data provides information on children receiving services but does not take into account the general population or all children with disabilities.

Autism and Developmental Disabilities Monitoring (ADDM) Network

A young boy smiling.

The Autism and Developmental Disabilities Monitoring (ADDM) Network is the largest effort to monitor autism spectrum disorders (ASDs) in the United States. This public health surveillance system aims to provide comparable, population-based estimates of the prevalence rates of autism and related disorders in different locations across the U.S. The data are collected every two years using the same methods. ASD prevalence is determined through the review of health and education records in collaboration with state health departments, diagnostic facilities, and school systems.

Evaluating prevalence trends of ASDs can be difficult for several reasons. Until very recently, few data were systematically collected from the same groups of people over time. Although the available data appear to show an increase in prevalence, this increase may be due in part to changes in ASD definitions and diagnoses, increased public awareness, or the availability of resources and diagnostic tools, among other possibilities.

Articles and reports:

Article: Prevalence of Autism Spectrum Disorders, 2006

Read a full report on the 2006 ADDM findings >>

Read a full report on the 2000 and 2002 ADDM findings >>

What data are collected and how?

A doctor holding a teddy bear, talking to a young boy.

A child is classified as having an ASD if he or she displays behaviors consistent with diagnostic criteria for Autistic Disorder, Pervasive Developmental Disorder-Not Otherwise Specified (including Atypical Autism), or Asperger's Disorder. Identifying an ASD in a child should be done by a qualified professional. Identification criteria can be found in the Diagnostic and Statistical Manual of Mental Disorders - Fourth Edition, text revision (DSM-IV-TR). Read more about evaluation criteria.

A panel of clinicians reviews the records of the identified children to ensure they meet the requirements of the monitoring program and should be considered as having an ASD. Within a state, ADDM data may only include information for one or a few counties or cities and may not be representative of the entire state.

Limitations of the data and measures

  • No medical test exists for ASDs. Diagnosis typically is made after an evaluation including clinical observations, parent interviews, developmental histories, psychological testing, speech and language assessments, and possibly the use of one or more autism diagnostic tests.
  • Diagnostic criteria for autism and related disorders must rely on behavioral observations of development. This makes describing the population of people with ASDs challenging, especially because the criteria for diagnosing ASDs have changed over time.
  • The ADDM locations do not make up a nationally representative sample, and caution is needed when generalizing rates to every community in the United States.
  • Not all ADDM Network data collection locations have access to education records (in addition to health records). These sites underestimate prevalence of ASDs.

Department of Education (ED) - Individuals with Disabilities Education Act (IDEA)

A teacher talking in sign language to her students.

The Individuals with Disabilities Education Act is a law ensuring services to children with disabilities throughout the nation. IDEA governs how states and public agencies provide early intervention, special education, and related services to more than 6.5 million eligible infants, toddlers, children, and youth with disabilities.

Infants and toddlers with disabilities (birth-2 years) and their families receive early intervention services under IDEA Part C. Children and youth (ages 3-21) receive special education and related services under IDEA Part B.

Disabilities included in IDEA data are:

  • Autism
  • Deafness and blindness
  • Developmental delay
  • Emotional disturbance
  • Hearing impairments
  • Intellectual Disabilities (formerly Mental Retardation)
  • Multiple disabilities
  • Orthopedic impairments
  • Other health impairments
  • Speech or language impairments
  • Specific learning disabilities
  • Traumatic brain injury
  • Visual impairments

Data sets for all of these developmental disabilities are available on an IDEA website.

What data are collected and how?

Annually, all states are required to submit data to the Department of Education on the number of children with disabilities receiving special education and related services (see Section 618 of IDEA for all required data elements). Data include age, race, ethnicity, gender, and disability. Children with more than one primary disability are reported as "multiple disabilities." Not all states use all disability categories. The use of the disability category "developmental delay" is optional for states for children ages 3 through 9. These data are collected to ensure that public agencies meet program requirements and to improve education results and functional outcomes.

Limitations of the data and measures

A young boy standing next to a math equation on a chalkboard.

Data collected are for children receiving services and do not reflect the general population. These data can be used to determine the number of children receiving services for developmental disabilities. However, these data cannot be used to estimate prevalence of any given disability among the general population for the following reasons.

  • The number of children with a given disability who are not receiving services and are not included in the data is unknown.
  • Children with certain disabilities may be more likely to receive services than others.
  • In addition, special education disability labels are used to indicate educational need and not a diagnosis of a specific condition.

These data should not be compared across states for type of disability because eligibility criteria vary across states. Eligibility policies within a state may change, so year-to-year comparisons should be completed with caution. Funding and availability of services for a state can affect state eligibility policies; when state economies are strained, state eligibility criteria may become more narrow and show an associated decrease in the number of children identified with disabilities.

Other data sources

Two other national surveys provide some information on developmental disability prevalence. The National Survey of Children's Health and the National Health Interview Survey ask caregivers if a doctor or healthcare provider ever told them that their child has one of a few select developmental disabilities. These surveys provide nation-wide estimates of reported developmental disabilities. Data from these surveys are not included on the Tracking Network at this time, but content from these surveys has been used to provide context for this topic.

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