Mental Retardation/intellectual deficit disorder · Uncategorized

Understanding Intellectual Deficit Disorder (IDD)

Look up intellectual deficit disorder (IDD) in a dictionary and you’ll find the following: “A person with IDD (formerly mental retardation) struggles with an intellectual disability and has difficulties with adaptive functioning.  The illness always starts before the age of 18.”  That’s the formal definition, but what does it mean?  Here’s an overview:

What are intellectual disability and adaptive problems?

Intellectual disability  

Intellectual disability is when a person has a below-average intelligence.*   Average IQ is 100.  A score lower than 70 is usually considered IDD.

option--paper-kitPsychological tests determine a person’s intellectual capacity.  One common neurocognitive test is the Wechsler Intelligence Scale for Children Fifth Edition (WISC).  It’s used for kids 6-11 and takes 45 to 65 minutes to administer.  The WISC assesses a bunch of thinking and memory tasks, including the ability to juggle information in one’s head, learn, reason, make decisions, remember things, understand and process words, solve problems, and much, much more.

There is a version of the Wechsler for adults.  However, when a person starts having chronic cognitive deficits after age 18, the diagnosis is usually dementia.  Here’s an example question typical of the adult Wechsler test (borrowed from the article “Working Memory and Fluid Reasoning: Same or Different,” Scientific American):

Can you identify the missing piece in the pattern?  Choose from 1-8.

(The correct answer is 5.  No worries if it took you a while, you’re not getting dementia!  These exams aren’t easy.)

* For a closer, nontraditional look into how IQ and intelligence aren’t always the same thing, check out the article, Why you can have a low IQ but still be amazingly smart.

Adaptive problems. 

While IQ refers to intellect, adaptive abilities is about skills. People with IDD have difficulties taking care of themselves in day-to-day life.  They have limited skills.  This might include expressing needs, communicating with and understanding others, or challenges with basic tasks like feeding, bathing, and dressing.

In adults with IDD, adaptive skills determine one’s ability to live independently, study, work, handle money, carry on intimate relationships, raise children, and make medical/legal decisions.  Like IQ, level of function is assessed by formal adaptive behavior assessments.

Note that a person with an IQ of 65 might have normal social or communication adaptive functioning, meaning they don’t have IDD!

What are the different types of IDD?


There are hundreds, if not thousands, of causes of IDD.  Some involve the genes, like Down’s and Fragile X Syndromes.  These are the most common.  Medical problems while in the uterus and during birth can cause problems, like infection, exposure to drugs or alcohol, trauma, low oxygen, and malformations.  Illness during childhood can also lead to IDD, like meningitis, exposure to heavy metals, vitamin deficiency/malnutrition, thyroid problems, and traumatic brain injury.  Other causes include cerebral palsy, untreated hydrocephalus, Sometimes there is no clear explanation for why a child falls prey to IDD.

Causes of IDD
Causes of Intellectual Deficit Disorder, or IDD (image courtesy of Aegyo Kawaii’s blog Intellectual Disability)

Levels of severity.

Regardless of the cause, people with IDD have varying degrees of disability, ranging from mild to very severe.  Severity is determined by adaptive abilities, not IQ.

  • Mild.  IQ typically 50-70.  People with the mild form usually reach a 6th grade level of function.  They have good verbal abilities.  They can take care of themselves, live alone or in group homes, and sometimes hold a simple job. They often blend in socially.  About 85% of people with IDD fall into this group.
  • Moderate.   IQ usually 35-49.  People with moderate IDD tend to function at a 2nd grade level; they need more supervision than a person with mild IDD and typically live in group homes.  They can take care of their basic needs but require support for complicated tasks.
  • Severe.  IQ usually 20-34.  Individuals at this level usually require 24-hour supervision.  They’re unable to take care of themselves without much prompting and don’t go to school.  Often they understand basic speech but have difficulty communicating with words.
  • Profound.   IQ usually less than 20.  People with profound IDD need help meeting all needs, including toileting, eating, and communicating.
What’s the difference between IDD and autism? 

A person with autism has difficulties in two specific areas: verbal & nonverbal communication, and repetitive obsessions/mental rigidity.  They may have a normal IQ and function successfully in the community.  These individuals would be called “high-functioning autistics” and possibly have Asperger’s Syndrome.  Alternatively, someone with autism may have a low IQ plus significant adaptive challenges, and be diagnosed with both autism and IDD.

Other symptoms of autism include:

  • Disinterest in social interaction
  • Difficulty reading nonverbal cues and understanding “social rules”
  • Problems seeing things from other people’s point of view
  • Poor or inappropriate, pedantic, or monotone speech
  • Oversensitivity to noise, materials/textures, taste, touch
  • Difficulty dealing with change in routine/ritual
  • Narrow, obsessive, strange interests (like fascination with doorknobs)
What treatments are available? 

There is no cure.  Affected children often need special education with focus on self-care, communication, structure, and social skills.  They also benefit from individual and family counseling.  Children with IDD should have regular visits with their pediatrician.

Once adults, people with intellectual deficits need continued support to maintain housing, occupy their time, make good decisions, and function on a day-to-day basis.  Sometimes this means living in a group home or special residential setting.  Assistance with education and finding a part-time work would be an important part of the treatment for a person with mild IDD.

If needed, medications can help with depression, anxiety, attention problems, agitation, self-abusive behaviors, and other psychiatric symptoms/disorders.

Here’s more information on treatment modalities:

Treatment for Intellectual Deficit Disorder, IDD (borrowed from Jayesh Patidar’s nursing lecture, Mental Retardation)


How can a caregiver help their loved one with IDD? 

Families and friends of people with IDD often find themselves overwhelmed and unsure where to go for help.  Here are some tips to help you along the way:

  • First, educate yourself about your loved one’s specific condition.  There are many types of IDD, and each one has its nuance.
  • Use rewards for good behavior.  Consider stickers, food, music, or video games.  Reward at short intervals and slowly lengthen.
  • Use distraction/redirection to pull them away from less-than-good behavior.
  • Avoid lengthy verbal monologues and abstract explanations.
  • Use “hands on” and visual aides to help with learning.
  • Break tasks up into small steps.
  • If you need help, reach out to other family or friends for help.  Alternatively touch basis with your loved one’s doctors, who might have ideas to increase support.  Thirdly, consider doing an online search for “respite care.”  There are many respite services available to families.
  • If behavioral problems are an issue, consider taking your family member to see a psychiatrist.
  • Remember, you aren’t good to anyone if you don’t take care of yourself!

For more information on IDD and other developmental disorders, look at the American Association of Intellectual and Developmental Disabilities‘ webpage.


One thought on “Understanding Intellectual Deficit Disorder (IDD)

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s