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. These two sources provide different kinds of data.

CDC's Autism and Developmental Disabilities Monitoring (ADDM) Network

Tracking Network data on the prevalence of autism spectrum disorders (ASDs) and other developmental disabilities come from the ADDM Network. The ADDM Network provides the number of existing cases of ASDs in a defined population.

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's Individuals with Disabilities Education Act (IDEA)

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). The IDEA data provide information on children receiving services but do not take into account the general population or all children with disabilities.

Limitations of the data and measures:

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.

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