Intellectual Disability/Intellectual Development Disorder (IDD)

Intellectual Disability

Deficits in both intellectual abilities and life functioning through three domains: conceptual, social, and practical

• Intellectual abilities include: reasoning, problem solving, planning, abstract thinking, judgement, academic learning, and learning from experience

  • Generally have an IQ of 70 or below

• Life functioning: activities of daily life such as communication, social participation, and independent living

Onset and Severity

• Onset during developmental period

• Four levels of severity: mild, moderate, severe, profound

Mild Severity

• 85% of ID population

• 3rd-6th grade skill level in reading, writing, and math; may be employed and live independently

Moderate Severity

• 10% of ID population

• basic reading and writing skills; functional self-care skills; requires some oversight

Severe Severity

• 5% of ID population

• functional self-care skills; requires oversight of daily environment and activities

Profound Severity

• <1% of ID population

• may be able to communicate verbally or nonverbally; requires intensive oversight

Theories of ID

Genetics can lead to deficits seen in ID

Phenylketonuria (PKU)

Unable to metabolize phenylalanine (amino acid); diet can help

Tay-Sachs Disease

Progressive degeneration of nervous system: early death

• prominently seen in jews

Down syndrome (Trisomy 21)

3 chromosome 21s; neural abnormalities

fragile X syndrome

Tip of X chromosome breaks off; speech and interpersonal deficits

Trisomy 13

3 chromosome 13s

Trisomy 18

3 chromosome 18s

Theories of ID: Brain

• prenatal exposure to viral infections such as rubella, herpes, and syphils

• chronic maternal disorders: high blood pressure, diabetes

• Exposure to toxic substances (lead, arsenic, mercury)

• traumatic brain injury

Fetal Alcohol Syndrome (FAS)

Poor judgement, distractibility, and social deficits in children, academic deficits in adolescence

Severe Head Trauma

Shaken baby syndrome

Sociocultural Factors

• Low socioeconomic background

  • Parent with ID, leads to lower paying jobs

  • less prenatal care leading to more birth complications

  • increased exposure to lead

  • poorly funded schools, so less assistance for low IQ students

  • less educational exposure at young age (books, educational toys, etc)

Early Intervention Programs

Enhance development of basic skills and reduce interfering social conditions

Mainstreaming

In regular classrooms vs. special education classrooms

Group Homes

Assistance with daily living skills/tasks, vocational training, social skills training; may work in sheltered workshops or mainstreamed into general workforce