ID, DD, and Cognitive Disabilities.

I’ve noticed a trend of using Intellectual Disability (ID), Developmental Disability (DD), and Cognitive Disability interchangeably. I find this extremely problematic, and wanted to suggest some guidelines as to what these terms mean

Developmental Disability– The Administration on Developmental Disabilities defines a DD as something that, starting before the age of 22, impairs or alter’s one’s ability to perform 3 or more certain major life activities listed on their page. They also state that it can be either physical or mental. (What is a Developmental Disability?) On a page that is designed for bureaucratic rather than accessible language, they elaborate that this means life-long disabilities that are “likely to continue indefinitely.” (OPD’s Factsheet on the Administration on Developmental Disabilities.)

What sort of Disabilities are included? While IDs aren’t uncommon, DDs include disabilities which might or might not have any ID co-morbidities () such as Cerebral Palsy and Autism Spectrum Disorders*.  There is a tendency to assume that if an individual has a DD they must have an ID, but this is a stereotype. It is built in part on the fact that some DDs effect the ability to communicate in a typical fashion, and so early work in the field assumed certain things about the intelligence of those with DDs as a whole.

Basically while a lot of people who fall under the DD label also have IDs, Having an ID isn’t a necessary part of having a DD.

Cognitive Disability– Cognitive Disabilities are not the same as Intellectual Disabilities, either. Cognition- while a part of intelligence**- is not exclusively intelligence. It also includes how we learn, and how we organize ideas.

I like how Opera defines Cognitive Disabilities:

These conditions affect a web user’s ability to perform one or more mental tasks. This includes problems with:

  • reading text
  • memory
  • problem solving
  • keeping focused (attention span)
  • computation (for example calculations)
  • non-verbal learning (for example difficulty with written materials)

(Opera’s Web Accessibility for Cognitive Disabilities and Learning Disorders.) Executive Functioning difficulties fall under this concept of Cognitive disabilities.

The most common alternate for this tends to be Learning Disabilities. I think it’s important to note that this includes the executive functioning issues in those with ADD/ADHD. Other examples of Cognitive Disabilities that aren’t always covered under IDs include Dyslexia, Dyscalculia, and even Traumatic Brain Injury (TBI). Additionally, TBI generally isn’t considered a DD. (And, on a personal note, is my sister’s Dx.)

Intellectual Disability– When one thinks of the old classification “Mental Retardation”*** it typically is referring to those with IDs, even though the old label was sometimes used for DDs.

The Equal Employment Opportunity Commission (EEOC) and the ARC give the definition of Intellectual Disability as

Intellectual disability is a below-average cognitive ability with three (3) characteristics:

  1. Intelligent quotient (or I.Q.) is between 70-75 or below
  2. Significant limitations in adaptive behaviors (the ability to adapt and carry on everyday life activities such as self-care, socializing, communicating, etc.)
  3. The onset of the disability occurs before age 18.

(The Arc, Intellectual Disability.)  While I have issues with the way we measure Intelligence/IQ, this seems to be the most workable definition.

Some examples of those who may or may not have Intellectual Disabilities are those with Down Syndrome, Fetal Alcohol Spectrum Disorders, or Fragile X syndrome. The ARC also mentions that an estimated half of the population with Intellectual Disabilities do not meet the definition for having Developmental Disabilities.

In Closing

While one can have Intellectual, Cognitive, and Developmental Disabilities at the same time, they are not interchangeable terms. It is possible to have one without any of the others, only two, or all three types of disabilities.

This is true even when you are looking at people with the same dx. Though most people with Down Syndrome have IDs, not all do.  While FASD awareness (and services?) are under SAMHSA, those with it might also have IDs. Someone With Cerebral Palsy has a DD, but might only be effected physically. Those with ADHD have cognitive disabilities but might not have either ID or DD, though they could also have both.

So, please, keep in mind the population that you are talking about. When you are talking about having Autistics share their stories on your site, ID isn’t really the best term, because you cut/erase a heavy percentage of Autistics that way. When looking at website accessibility remember: just because the content isn’t something you can make ID accessible, doesn’t mean you can’t make it more cognitively accessible.


* Note that the National Institutes on Health site article linked above is using the Current DSM’s definition. The new DSM coming out merges Asperger’s Syndrome and PDD-NOS, though they are linked out as separate in the article linked above.

** Note: The concept of intelligence is considered flawed by many people. I am using it because it is the terminology/lingo that is used in both the advocacy and service provider communities. Additionally, I have seen references that the Education system lumps cognitive disabilities under Learning Disabilities, and uses cognitive disability to mean Intellectual Disability. . . I’m not so familiar with Education from the educators end. Feel free to let me know more in the comments.

*** I oppose the use of the R-word, however some government sites and some state/local systems still refer to themselves as MR services. This is the reason why “Mental Retardation,” in quotes, is mentioned. My own county, in fact, still refers to it as “MR”, usually in the jumble of human services that locals call “MH/MR.”


8 thoughts on “ID, DD, and Cognitive Disabilities.

  1. happypinkegg:

    Hmmmm… I have had different experiences with these terms.

    I work in special education with students with cognitive disabilities. Basically, according to my state, a person has a cognitive disability if their IQ is less than 70 and has difficulties with adaptive behaviors. This is what used to be classified as “mental retardation.”

    I had never heard of IDs before, and students whose IQs are between 70 and 75 are considered “slow learners” and are not considered to have a disability.

    Finally, I am familiar with DDs as a ‘catchall’ for students who have a disability (whether autism, ohi, CI, etc…) before 3rd grade. As of 3rd grade they need to be diagnosed with another disability in order to keep receiving sped. services.

    Nicocoer (me):

    I’ve only seen the first? And that was on a site for special educators. All my definitions come from Federal government sites, with the exception of the cognitive disabilities because I just couldn’t find it on there in a way that defined it- just in reference that x,y, and/or z would be considered a cognitive disability issue. Those I’ve talked to, particularly when it comes to policy people and services that aren’t Education such as neuropsychs, recognized those with LDs, IDs, and/or with executive functioning issues related to a disability as falling under the cognitive disabilities label.

    I’ve *never ever* heard that definition of developmental disability, even when talking to parents having issues with their school districts providing services. What state are you in? Is this in the policy books or training material, or is this how it was used in the school district? (I talk to a lot of parents, and this might be good to know…)

    I consider myself to fall under both Cognitive and Developmental Disabilities labels, but not the Intellectual Disabilities label. I have a Developmental Disability (I’m Autistic) and the effects of that are such that for me, it’s also a cognitive disability- I can’t hold numbers in my head correctly, I can’t get the phonetics right, I am easily visually over whelmed, have lots of difficulty with various executive functioning issues.

    In all honesty, education definitions are only really useful in that setting. The terminology differences between the fields is pretty big, and there have been cases where because of that, education folks have used studies done by Neuro Psych people in a way that was not accurate to their findings *because* of it. I know of one woman who would actually have a shouting match with people who used certain (other) words in a way that is not “proper” according to her research field, even though the colloquial and policy meanings were such that the user was correct in the context it was used in.

    I don’t know much about Special Education, at least not from the perspective of the educator. I know a good deal of it from the point of view of the student, though my level social awareness prevented me from being aware of the educator end. I do know that parents face a LOT of issues in dealing with their children’s schools because of the differences in terminology. I even know policy makers who were shocked at how their policy was interpreted by teachers- but then, most teachers and administrators aren’t versed in policy.

    Cross-specialty definitions seem like a huge barrier between the education system and the other systems, including the federal policy writers.


    nicocoer (me) asked:

    Is it okay if I copy this (Re: ID, DD, CD) discussion over to the comments in the actual blog itself?

    Happypinkegg replied:


    BTW I live in Illinois and those are the definitions set by the state. But as you are probably aware, names change. Just a couple years ago ‘cognitive impairment’ was ‘mental impairment’ and before that ‘mental retardation.’ So, there’s that…

    But those are the current definitions for qualifying for services. As I mentioned, after grade 3 a student needs to be identified as having a specific disability (autism, adhd, etc…) and not DD.

    nicocoer (me) replied:

    Re: DD- oh, I thought they stopped considering it a DD after that point. I consider these to be classifications of disabilities, not a Dis in and of itself. There’s a reason for LD-NOS & PDD-NOS &c being dxs. having a dx makes sense.

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  5. Thank you for this. I’m a para in a high school that assigns students to teachers based on the particular disability. One teacher might case manage ‘EBD’ students, another ‘ID’ and another ‘CD’ … I was confused about the latter two.

    • ID in the US means intellectual disability, usually defined by IQ. In the UK, this is usually called “learning disability”

      In the US, “learning disability” doesn’t have to involve IQ, it’s simply disabilities that impact learning, such as dyslexia and dyscalclia.

      I think CD might mean cognitive disability, which MIGHT include US LDs, as well as other cognitive things but I’m not sure. CD in non-education contexts usually involves a broad range of cognitive impairments, not just (US definition) LDs.

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