Saturday, March 6, 2010

Major Types of Disabilities

As described in a separate post, I was trying to figure out what "the disability community" meant.  I wondered if it was based on different types of disabilities, so I did a search for that.  Figuring out the major types of disabilities turned out to be a pursuit of its own, as described in this post.

My search for "types of disabilities" yielded thousands of hits.  I looked at a few that appeared near the top.  It appeared that there was not one commonly accepted list of types of disabilities.  There seemed to be a couple different kinds of entries on these lists.  First, there were the ones that seemed to be included on most lists, such as vision, hearing, learning, and psychiatric disabilities.  Then there were some that appeared on some lists but not others, including dwarfism, ADD/ADHD, and seizures.

The Office of Student Disability Services at Johns Hopkins University provided one of the lists that I looked at.  Johns Hopkins is, of course, world-famous in medical education.  I assumed that their list would tend to be relatively coherent in light of current knowledge.  I was surprised, though, that they treated ADD/ADHD as a separate major type of disability, when the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) included it within the set of psychiatric disorders.  I suspected Johns Hopkins broke it out separately because their webpage was especially focused on disabilities that would affect college students.  I thought this might also be why their list did not mention developmental disabilities.

Since none of the pages that I looked at seemed to be drawing from any common source of knowledge, I decided I had better search some more.  I did a more refined search for types of disabilities and was belatedly reminded of the World Health Organization's (WHO) International Classification of Functioning, Disability and Health (ICF).  I had not previously paid much attention to the ICF, but now seemed like a good time to learn a bit more about it.

As I discovered, the ICF identifies four categories of functioning (i.e., ability, not disability), each of which is sometimes referred to by a single letter.  Those four categories are Body Functions (b), Body Structures (s), Activities and Participation (d), and Environmental Factors (e).  Then there are numbered categories under each of those.  So, for instance, someone who was nearsighted would apparently have an issue under Body Functions (b), Chapter 2 (Sensory Functions and Pain) (b2).  More precisely, they would be under b210-b229 (Seeing and related functions), under b210 (Seeing functions), under b2100 (Visual acuity functions):  b21000 (Binocular acuity of distant vision).  In other words, the code for nearsightedness would apparently be b21000, which reads as follows:  "Seeing functions of sensing size, form and contour, using both eyes, for objects distant from the eye."  A nearsighted person would have an issue with that particular aspect of normal functioning.

According to Hendershot, Placek, and Goodman (2006), there were 1,494 codes in the ICF.  The purpose of the ICF seemed to be to provide a comprehensive diagnostic tool.  People -- in the U.S., at least -- did not presently seem to be sorting major types of disabilities according to their ICF chapters and subsections.  So I decided it was not my best source of a good list of the major types of disabilities.

I reconsidered the Johns Hopkins list.  Wikipedia informed me that what is called "developmental disabilities" in the U.S. can be called "learning difficulty," "intellectual disability, or "cognitive disability" in other countries.  So perhaps it was not necessary to have developmental disabilities as its own major type of disability; maybe it could be included in one or more of the others.  As I looked again at the Johns Hopkins list, I also wondered about brain injuries.  Couldn't they be included under physical disabilities?  They said, "A variety of physical disabilities result from congenital conditions, accidents, or progressive neuromuscular diseases," and they mentioned stroke as one of the conditions they were talking about.  That view of physical disabilities certainly sounded like it would include brain injuries.  They also said, "Traumatic brain injury typically results from accidents; however, insufficient oxygen, stroke, poisoning, or infection may also cause brain injury."  So it did seem that brain injuries were a type of physical disability.

But in that case, physical disabilities might also include problems of hearing, vision, and speech, as well as medical disabilities; and learning disabilities could include language problems.  It looked like a person could boil down the major types of disabilities to just three, or maybe just two:  physical and mental.  So why weren't people doing that?

Plainly, the experts were aware that the causes, locations, symptoms, and other features of various disabilities overlapped quite a bit.  They seemed to be trying to divide them out, not put them together.  The experts were developing things like the DSM and the ICF, with endless distinctions among disabilities; they weren't bickering about two or five or ten main categories.  The lists that I had been looking at were inconsistent with one another because the really knowledgeable people weren't involved with them.  They weren't trying to come up with the world's best list of top categories.  In a sense, this began to look like nothing more than a matter of semantics, for people who didn't know any better.

Well.  If the purpose of a list of major types of disabilities was just to give ordinary people something to work with in everyday life, we seemed to have already accomplished that.  According to the Lay Person's Categorization of Dysfunctionality, as expressed in plain English, we had a matrix structure of disability differentiation.  First, there was the kind of disability (e.g., blind, deaf, uses a wheelchair), and then there was its intensity, along a spectrum from "people hardly notice it" through "disabled" to "he's gonna die."

To develop a better vocabulary of disability categorization for ordinary usage, one that almost everybody could grasp and use, it seemed that it might be necessary to disregard the complex diagnostic schema of the DSM and the ICF, and focus instead on finding an approach that would help to generate appropriate levels of community understanding and support for people with disabilities.  I hoped to move in that direction as I continued to explore the world of disabilities.