March is recognized as Intellectual/Developmental Disabilities Awareness Month, so we thought this would be a great time to explain what we mean by “Intellectual/Developmental disabilities (IDD).” Because the definitions of IDD can vary state-by-state and federally, we will talk about IDD here in general, practical terms. If you are interested in the specifics of statutes and rules, you can follow these links to read more about Colorado’s definition, Colorado’s rule change, and the Federal IDEA definition for a child with a disability.
Intellectual and Developmental disabilities refer to two disability groupings. “Developmental disability” is the broader, umbrella term and includes (but is not limited to) “Intellectual disability.”
Developmental disabilities (DD) are a group of conditions due to a delay or impairment in cognitive ability, physical functioning, or both.
These delays begin during the developmental period (in utero until end of adolescence) and will likely last throughout a person’s lifetime. These disabilities affect the path of the individual’s physical, learning, language, or behavioral development and may likely affect day-to-day functioning. 
Some Developmental disabilities are:
1) solely physical, such as blindness from birth;
2) some are both cognitive and physical, often true for people with Down syndrome;
3) and other developmental disabilities only affect cognitive abilities. In some cases, this is termed “Intellectual disability.”
Because of the diversity of ability under the umbrella of Developmental disabilities (DD), not all Developmental disabilities are considered Intellectual/Developmental disabilities.
Intellectual disability (ID) is the most common developmental disability. Children and adults with an ID have significant difficulties in both intellectual functioning (communicating, learning, problem solving) and adaptive behavior (everyday social skills, routines, hygiene).  Originally, this type of disability was identified through the use of Intelligence Quotient (IQ) testing. It was generally accepted that an IQ score of 70 or lower identified a person as having an intellectual disability.
As with most things in life, Intellectual disabilities are on a spectrum. The disability can be mild or more severe. Most people with ID (85%) have mild intellectual disabilities, live fairly self-sufficient lives, and may be difficult to identify in everyday life. While this may help with the idea of inclusion, it also can cause additional problems such as lack of access to resources, unemployment, and problems with law enforcement due to being misidentified or misunderstood.
So why do we say “IDD”?
When we try to label and diagnose human beings in nearly any situation, it quickly becomes apparent that people don’t fit into boxes. Since there is a significant overlap between Developmental and Intellectual disabilities, and IQ tests are notoriously unreliable and biased against marginalized populations, legislators added an eligibility criteria called “adaptive behavior testing.” By looking at a person’s daily life challenges in a practical way, doctors and other diagnosticians can help identify people living with mild intellectual disabilities who may not have otherwise been identified. Therefore, we communicate about this diverse group of people as people who have Intellectual/Developmental disabilities (IDD).
Prevalence and Facts
1 in 6 children in the United States have some type of developmental disability.  This includes ADHD and learning disabilities. 
When the definition of Developmental disability is more refined and does not include ADHD or other learning disabilities, the rate of DD in the United States is around 6%. 
2-3% of Americans have some form of an Intellectual disability when the determination is based on an IQ score of 70 or lower. 
Cerebral Palsy (CP) is the most common motor disability in childhood. 
Intellectual Disability is the most common developmental disability. 
Males are more likely to be diagnosed with a developmental disability. 
Developmental disabilities occur among all racial, ethnic, and socioeconomic groups. 
Males are twice as likely to have any Developmental disability (DD) than females. 
Children living in poverty are more likely to have a Developmental disability. 
If you or someone you care about is wondering if you may have an Intellectual/Developmental Disability, read more here and let us know if you’d like to talk with an ACL Advocate to explore your options.
1. Centers for Disease Control and Prevention. (2019) Facts About Developmental Disabilities https://www.cdc.gov/ncbddd/developmentaldisabilities/facts.html#ref
2. National Institute on Health. (2010) FACT SHEET - Intellectual and Developmental Disabilities. Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
3. American Academy of Pediatrics. June 2011, VOLUME 127 / ISSUE 6. Trends in the Prevalence of Developmental Disabilities in US Children, 1997–2008. Coleen A. Boyle, Sheree Boulet, Laura A. Schieve, Robin A. Cohen, Stephen J. Blumberg, Marshalyn Yeargin-Allsopp, Susanna Visser, Michael D. Kogan
4. Disability Scoop. November 29, 2017. CDC Says Developmental Disabilities Are On The Rise. Heasley, Shaun. Retrieved from https://www.disabilityscoop.com/2017/11/29/cdc-disabilities-rise/24468/
5. American Psychiatric Association's Diagnostic and Statistical Manual (DSM-IV, APA, 2000)
6. American Academy of Pediatrics. (2015) Section on Developmental and Behavioral Pediatrics (SODBP) Retrieved from https://www.healthychildren.org/English/health-issues/conditions/developmental-disabilities/Pages/Intellectual-Disability.aspx
7. Centers for Disease Control and Prevention. (2019) Cerebral Palsy (CP) Retrieved from https://www.cdc.gov/ncbddd/cp/index.html