Citation Reference for Intellectual Developmental Disorder Node

According to the American Psychiatric Association, Intellectual Disability Disorder (IDD) has an overall general population prevalence of approximately 1%, though its prevalence rates vary by age. 

The prevalence of severe levels of IDD is approximately 6 out of 1,000 individuals. 

Prevalence of Intellectual Disability Disorder

The APA has four severity codes (degrees of IDD). 

1. mild
2. moderate
3. severe 
4. profound intellectual disability

APA's Severity Code for IDD

Risk and Prognostic factors (defined as the likely causes/factors which lead to the development of an ailment) of IDD include:

1. Prenatal aetiologies, such as genetic syndromes (ex. Variations in gene sequencing or copy number variants; chromosomal disorders)
2. Inborn metabolism errors
3. Brain malformations
4. Maternal disease (ex. Placental disease)
5. Environmental influences, such as alcohol, drugs, teratogens, or other toxins 
6. Labor and delivery-related events that may lead to neonatal encephalopathy (a disease of the newborn characterized by an inability to maintain respiration, in an altered state of consciousness, seizures, spasms, and poor tone)
7. Severe and chronic social deprivation
8. Toxic metabolic syndromes
9. Intoxications 
10. Low birthweight 
11. Premature births
12. Multiple births
13. Infections during pregnancy
14. Untreated newborn jaundice (a condition where the skin, whites of eyes, and mucus membranes turn yellow due to the inability of the liver to process red blood cells – though this is normal in newborn babies, it is supposed to be cleared after a day; untreated jaundice can cause a type of brain damage known as Kernicterus)


Risk and Prognostic Factors for IDD

Individuals with ID may have limited resources and access to health care which can result in a detrimental impact on their health.

Health in Individuals with Intellectual Disabilities (ID)

Reference for Savant Syndrome

Savant syndrome is a rare condition that exists in individuals with different developmental disorders but mostly in people with autism, this condition gives individuals remarkable mental abilities and skills such as being able to immediately calculate difficult numerical operations, calendar calculations, solve extremely difficult puzzles, artistic talents, and more.

Savant Syndrome

Intellectual Disability (ID), a term that has officially replaced 'mental retardation', is diagnosed based on criteria from the American Psychiatric Association’s DSM-5. A diagnosis requires deficits in both intellectual functions and adaptive functioning, with an onset during the developmental period. The three core criteria are: 

1. **Criteria A - Deficits in General Mental Abilities:** Confirmed through both clinical assessment and standardized intelligence testing (e.g., reasoning, problem-solving, academic learning). 

2. **Criteria B - Impairment in Everyday Adaptive Functioning:** Deficits that result in a failure to meet sociocultural standards for personal independence and social responsibility across various environments. 

3. **Criteria C - Early Onset:** The intellectual and adaptive deficits must begin during the individual’s developmental period.

Definition and Diagnostic Criteria of Intellectual Disability (ID)

An intellectual disability (ID), formerly known as mental retardation, is diagnosed when an individual meets specific criteria: earning a score approximately two standard deviations below the mean on an intelligence test (about 70 on a test with a mean of 100), having major deficits in adaptive functioning, and showing these cognitive and adaptive deficits before the age of 18.

Diagnostic Criteria for Intellectual Disability

Intellectual disability is classified into four subtypes: mild, moderate, severe, and profound. The specific criteria for each subgroup are listed in the Diagnostic and Statistical Manual of Psychological Disorders.

Subtypes of Intellectual Disability

Intellectual Developmental Disorder (Intellectual Disability) – the specific disorder, not general category – is recognized by deficits in both intellectual functions and adaptive functions that are present in conceptual, social, and practical domains of everyday life. The onset of these deficits is required to be during the developmental period. 

Cedarville University

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The DSM-5-TR separates Intellectual Developmental Disorders into the following specific disorders:
-	Intellectual Developmental Disorder (Intellectual Disability)
-	Global Developmental Delay
-	Unspecified Intellectual Developmental Disorder (Intellectual Disability)


[DSM-5-TR] List of Intellectual Developmental Disorders

Individuals with Intellectual and Developmental Disabilities

IDD 

American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.). https://doi.org/10.1176/appi.books.9780890425596

DSM-5

Spielman, R. M., Jenkins, W. J., & Lovett, M. D. (2020, April 22). Psychology (2nd ed.). OpenStax. https://openstax.org/books/psychology-2e/pages/1-introduction

OpenStax Psychology (2nd ed.) Textbook

Intellectual Developmental Disorder (Intellectual Disability)

Global Developmental Delay is a neurodevelopmental disorder that is diagnosed when there are significant delays in in several areas of development related to intellectual functioning, specifically for children under the age of 5. This diagnosis is also applied to individuals who are unable to participate in systemic assessments, including those who are too young. This diagnosis should be reassessed in the individual later life. 

Global Developmental Delay

CB are displayed by up to 60% of the adult IDD population. Example behaviors include physical aggression toward others including self (self-injurious) and property, and verbal aggression. 

CB may be difficult to manage as it can cause stress to the individual, their families, and those around them. It can also lead to restrictive practices as well as loss of community based placements. This can lead to hospitalization and a limited access to long term care facilities.


Challenging Behaviors (CB)

Early
  - Apathy 
  - Withdrawal

Late
 - Severe intellectual deterioration
 - Marked Changes in Personality and Mood
 - Loss of Sphincter Control
 - Onset of epileptic seizures 
 - Loss of mobility with increased muscle tone
 - Eventual complete loss of all self-help skills

Common Early and Late Symptoms of Dementia in individuals with IDD

Intellectual Developmental Disorders (Intellectual Disabilities) are recognized through deficits in general mental abilities. These include reasoning, problem solving, planning, abstract thinking, judgement, academic learning, and learning from experience. These deficits can result in impairments of adaptive functioning, causing the individual to not meet standards of personal independence and social responsibility in one or more aspects of daily life. These aspects include communication, social participation, academic or occupational functioning, and personal independence at home or within the community. 

Intellectual Developmental Disorders

Health of Individuals with Intellectual and Developmental Disorders

Saxena, M., & Adamsons, K. (2013). Siblings of Individuals with Disabilities: Reframing the literature through a bioecological lens. Journal of Family Theory & Review, 5(4), 300–316. https://doi.org/10.1111/jftr.12021

Siblings of Individuals With Disabilities: Reframing the Literature Through a Bioecological Lens


Siblings of Individuals with Disabilities

It is estimated that there are 300,000 individuals with developmental disabilities in the United States.

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