What is DD? (And other terms you should know)

What are developmental disabilities?

Developmental disabilities originate at birth or during childhood and are characterized by impairments in both intellectual functioning (reasoning, learning, problem solving) and adaptive behavior (social and practical skills). They are substantial and are likely to continue indefinitely.

The term includes diagnosed conditions of intellectual disability, cerebral palsy, epilepsy, autism, and others.

But most important, people with developmental disabilities are our family members, neighbors, friends, classmates and co-workers.

Government has different definitions, from the broad definition used by the Centers for Disease Control, which your doctor may use, to narrow definitions intended to identify those most in need of long-term supports. Advocates also have their definitions.

The Developmental Disabilities Assistance and Bill of Rights Act (federal law; prevalence rate 1.58%):

"Developmental disability is a severe, chronic disability which:

  • Originated at birth or during childhood, is expected to continue indefinitely, and substantially restricts the individual's functioning in several major life activities.

More specifically, a developmental disability is a severe, chronic disability which:
  • Is attributable to a mental or physical impairment or a combination of mental and physical impairments;
  • Is manifested before the person attains age 22;
  • Results in substantial functional limitations in three or more of the following areas of major life activity:
        receptive and expressive language
        capacity for independent living, and
        economic self-sufficiency;
  • Reflects the person's need for a combination and sequence of special, interdisciplinary, or generic care, treatment, or other services which are of lifelong or extended duration and are individually planned and coordinated;
  • Except that such term when applied to infants and young children means individuals from birth to age five, inclusive, who have substantial developmental delay or specific congenital or acquired conditions with a high probability of resulting in developmental disabilities if services are not provided.

Washington state definition (RCW 71A.10.020)

"Developmental disability" means a disability attributable to intellectual disability, cerebral palsy, epilepsy, autism, or another neurological or other condition of an individual found by the secretary to be closely related to an intellectual disability or to require treatment similar to that required for individuals with intellectual disabilities, which disability originates before the individual attains age 18, which has continued or can be expected to continue indefinitely, and which constitutes a substantial limitation to the individual."

In its Washington Administrative Code (Chapter 388-823 WAC) the state goes on to define "substantial limitation" differently for different conditions.

  • For youth with intellectual disabilities, they need to test 2 deviations below mean in both intelligence tests and adaptive skills tests.
  • For autism, "substantial" means 2 deviations below the mean in adaptive skills, and 1 deviation below the mean in intelligence.
  • For cerebral palsy, neither intelligence nor adaptive skills are factors. The state looks at toileting, bathing, eating, dressing, mobility; or communication.
  • For epilepsy, the state requires the 2 deviations in adaptive behavior, but no deviation in intelligence.
Intellectual functioning refers to reasoning, learning and problem solving, while adaptive behavior refers to social and practical skills. Neither particularly captures challenges with communication some people with developmental disabilities struggle with. 

In 2022, the state legislature passed a law eliminating the use of IQ tests to determine eligibility for programs or services of the Developmental Disabilities Administration by 2025, so definitions for "substantial limitation" will change.


Centers for Disease Control and Prevention

Developmental disabilities are a group of conditions due to an impairment in physical, learning, language, or behavior areas. These conditions begin during the developmental period, may impact day-to-day functioning, and usually last throughout a person’s lifetime.

The Arc:

"Developmental disabilities are physical or mental impairments that begin before age 22, are likely to continue indefinitely, and result in substantial functional limitations in at least three of the following:

  • Self-care (dressing, bathing, eating, and other daily tasks)
  • Speaking and being understood clearly
  • Learning
  • Walking/mobility
  • Self-direction
  • Independent living
  • Economic self-sufficiency 
- Crafted in partnership with  the American  Association  on  Intellectual  and  Developmental  Disabilities (AAIDD), the American Network of Community Options and Resources (ANCOR), the  National  Association of Councils on Developmental Disabilities (NACDD), and United  Cerebral  Palsy (UCP)

What is developmental disability advocacy?

For The Arc, it is a effort of individuals with developmental disabilities, their families, service providers and community to promote and protect the rights of people with developmental disabilities and actively support their full inclusion and participation in the community.

“DD advocacy” is based on the belief that having a disability is a normal part of the human experience and in no way diminishes the rights of the individuals to contribute to society.

"Ableism" defines people by their disability and as inferior to the nondisabled, which reinforces discriminatory attitudes, social prejudice, and sets unwarranted limitations.

What are habilitative services?

Habilitative services help you keep, learn, or improve skills and functional abilities that may not be developing normally and are needed for daily living. Examples include therapy for a child who isn't walking or talking at the expected age.

Access to habilitative services is an ongoing issue, with too few receiving services either through Washington's Department of Social and Health Services' Developmental Disability Administration programs, or through insurance coverage.