Study Notes on Intellectual Disability (ID)

Distribution in the Population

  • Intellectual Disability (ID) affects 1% of the population.

  • In special education, it was 7.1% or 463,000 in 2009-10.

  • Male-to-female ratio: 1.6:1.

  • Higher prevalence in rural and low-income areas due to health access, stimulation, and nutrition issues.

Etiology of ID

  • Familial origin significant; most have IQs of 50-70.

  • Exceptions include undetected brain injuries.

  • Ethnic minorities and low SES show higher rates; causes can include brain injury and developmental malformations.

Federal Law/Regs

  • IDEA 2004 defines intellectual disability as significant sub-average intellectual functioning alongside adaptive behavior deficits, beginning in the developmental period.

  • Previous terminology: "mental retardation" replaced by "intellectual disability."

Texas Law ID Eligibility

  • Criteria include significantly sub-average functioning (IQ at least 2 standard deviations below mean) and deficits in adaptive behavior across specified domains.

DSM-5-TR ID Criteria

  • Criterion A: Deficits in intellectual functions confirmed by assessment. Scores typically are 2 standard deviations below mean (IQ < 70).

  • Criterion B: Deficits in adaptive functioning affecting everyday activities.

  • Criterion C: Onset occurs during the developmental period.

Alternate Diagnoses

  • Global Developmental Delay: For children under 5 when assessment is not feasible.

  • Unspecified Intellectual Disability: For children over 5 when assessment difficulties arise.

History of Terminology

  • Terminology transitioned from medical terms like idiot, imbecile to "intellectual disability," following Rosa's Law in 2010.

Severity Levels of ID

  • Mild: 55-69 IQ, 85% of cases; possible partial independence.

  • Moderate: 40-54 IQ, 10% of cases; requires support for daily activities.

  • Severe: 25-39 IQ, 3-4% of cases; daily care assistance needed.

  • Profound: IQ < 25, 1-2% of cases; complete dependency on caregivers.

Co-Occurring Conditions

  • Includes diseases (e.g., Fragile X, Down syndrome), environmental factors (e.g., toxins, malnutrition), and prenatal exposure (e.g., FAS, infections).

Interventions for ID

  • Interventions include early service mandates, psychological services, speech therapy, special education, in-home assistance, and various therapeutic approaches.