5
Intellectual Disability (Intellectual
Developmental Disorder)
Eric J. Mash
A. Wolfe
©David
Cengage Learning
2016
© Cengage Learning 2016
Intelligence and Intellectual Disability (ID)
• Prior to mid-19th century: children and
adults with intellectual disabilities were
ignored or feared even by the medical
profession
• Intellectual disability: a significant limitation
in intellectual functioning and adaptive
behavior which begins before age 18
© Cengage Learning 2016
Intelligence and Intellectual Disability
(cont’d.)
• In the mid-19th century: Samuel G. Howe
opened the first humanitarian institution in
North America
• By the 1940s: parents increased humane
care for their children
© Cengage Learning 2016
Intelligence and Intellectual Disability
(cont’d.)
• 1950: National Association for Retarded
Children was formed
• 1962: President John F. Kennedy formed
the President’s Panel on Mental
Retardation
© Cengage Learning 2016
The Eugenics Scare
• Evolutionary degeneracy theory
– Pervasive in 19th century
– Intellectual and social problems of children
with mental retardation were viewed as
regression to an earlier period in human
evolution
– J. Langdon H. Down interpreted “strange
anomalies” as throwbacks to the Mongol race
© Cengage Learning 2016
The Eugenics Scare (cont’d.)
• Eugenics: “the science dealing with all
influences that improve the inborn qualities
of a race” ~ Sir Francis Galton
– Led to the view that individuals with ID (moral
imbeciles, or morons) were threats to society
© Cengage Learning 2016
Defining and Measuring Children’s
Intelligence and Adaptive Behavior
• Alfred Binet and Theophile Simon (1900s)
– Commissioned by the French government to
identify schoolchildren who might need
special help in school
– Developed the first intelligence tests
• Measure judgment and reasoning of school
children (Stanford-Binet scale)
© Cengage Learning 2016
Defining and Measuring Children’s
Intelligence and Adaptive Behavior (cont’d.)
• General intellectual functioning is now
defined by an intelligence quotient (IQ or
equivalent)
• ID is no longer defined on the basis of IQ
– Level of adaptive functioning is also important
• Adaptive functioning: how effectively individuals
cope with ordinary life demands and how capable
they are of living independently
© Cengage Learning 2016
Specific Examples of Adaptive Behavior
Skills
© Cengage Learning 2016
The Controversial IQ
• IQ is relatively stable over time
– Except when measured in young, normallydeveloping infants
• Mental ability is always modified by
experience
• The Flynn Effect: the phenomenon that IQ
scores have risen about three points per
decade
• Are IQ tests biased or unfair?
© Cengage Learning 2016
Features of Intellectual Disabilities
• Clinical description - considerable range of
abilities and interpersonal qualities
– DSM-5 diagnostic criteria
• Deficits in intellectual functioning
• Concurrent deficits or impairments in adaptive
functioning
• Below-average intellectual and adaptive abilities
must be evident prior to age 18
© Cengage Learning 2016
Diagnostic Criteria for Intellectual Disability
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Severity Level: Mild
• About 85% of persons with ID
• Typically not identified until early
elementary years
• Overrepresentation of minority group
members
• Develop social and communication skills
• Live successfully in the community as
adults with appropriate supports
© Cengage Learning 2016
Severity Level: Moderate
• About 10% of persons with ID
• Usually identified during preschool years
• Applies to many people with Down
syndrome
• Benefit from vocational training
• Can perform supervised unskilled or
semiskilled work in adulthood
© Cengage Learning 2016
Severity Level: Severe
• About 3%-4% of persons with ID
• Often associated with organic causes
• Usually identified at a very young age
– Delays in developmental milestones and
visible physical features are seen
• May have mobility or other health
problems
– Need special assistance throughout their lives
– Live in group homes or with their families
© Cengage Learning 2016
Severity Level: Profound
• About 1%-2% of persons with ID
• Identified in infancy due to marked delays
in development and biological anomalies
• Learn only the rudimentary communication
skills
• Require intensive training for:
– Eating, grooming, toileting, and dressing
behaviors
• Require lifelong care and assistance
© Cengage Learning 2016
Examples of Support Areas
© Cengage Learning 2016
Prevalence
• Approximately 1-3% of population
(depending on cutoff)
• Twice as many males as females among
those with mild cases
• More prevalent among children of lower
SES and children from minority groups,
especially for mild cases
– More severe levels - identified almost equally
in different racial and economic groups
© Cengage Learning 2016
Factors Accounting For Racial Differences
© Cengage Learning 2016
Developmental Course and Adult Outcomes
• Developmental-versus-difference
controversy
– Do all children—regardless of intellectual
impairments—progress through the same
developmental milestones in a similar
sequence, but at different rates?
• Developmental position
– Similar sequence hypothesis
– Similar structure hypothesis
© Cengage Learning 2016
Developmental-Versus-Difference
Controversy (cont’d.)
• Difference viewpoint: cognitive
development of children with ID is
qualitatively different in
reasoning/problem-solving
– Familial versus organically based ID
© Cengage Learning 2016
Motivation
• Many children with mild ID are able to
learn and attend regular schools
• Often susceptible to feelings of
helplessness and frustration in their
learning environments
• Children who have mild ID are able to stay
on task and develop goal-directed
behavior
– With stimulating environments and caregiver
support
© Cengage Learning 2016
Changes in Abilities
• IQ scores can fluctuate in relation to the
level of impairment
• Major cause of ID affects the degree to
which IQ and adaptive abilities may
change
• Slowing and stability hypothesis
– IQ of children with Down syndrome may
plateau during middle childhood, then
decrease over time
© Cengage Learning 2016
Language and Social Behavior
• Development follows a predictable and
organized course
• Characteristics displayed with Down
syndrome
– The underlying symbolic abilities of children
are believed to be largely intact
– There is considerable delay in expressive
language development; expressive language
is weaker than receptive language
© Cengage Learning 2016
Characteristics Displayed With Down
Syndrome (cont'd.)
• Fewer signals of distress or desire for
proximity with primary caregiver
• Delayed, but positive, development of selfrecognition
• Delayed and aberrant functioning in
internal state language
– Reflects emergent sense of self and others
• Deficits in social skills and social-cognitive
ability; can lead to rejection by peers
© Cengage Learning 2016
Emotional and Behavioral Problems
• Rate is three to seven times greater than
in typically developing children
– Largely due to limited communication skills,
additional stressors, and neurological deficits
• Most common psychiatric diagnoses:
– Impulse control disorders, anxiety disorders,
and mood disorders
• Internalizing problems and mood disorders
in adolescence are common
© Cengage Learning 2016
Emotional and Behavioral Problems
(cont'd.)
• ADHD-related symptoms are common
• Pica is seen in serious form among
children and adults with ID
• Self-injurious behavior (SIB)
– Can be life-threatening
– Affects about 8% of persons across all ages
and levels of ID
© Cengage Learning 2016
Other Physical and Health Disabilities
• Health and development are affected
• Degree of intellectual impairment is a
factor
• Prevalence of chronic health conditions in
ID population is much higher than in the
general population
• Life expectancy for individuals with Down
syndrome is now approaching 60 years
© Cengage Learning 2016
Chronic Health Conditions Among Children
With Intellectual Disabilities
© Cengage Learning 2016
Causes
• Scientists cannot account for the majority
of cases, especially the milder forms
• Genetic or environmental causes are
known for almost two-thirds of individuals
with moderate to profound ID
© Cengage Learning 2016
Prenatal, Perinatal, and Postnatal Causes
• Prenatal: genetic disorders and accidents
in the womb
• Perinatal: prematurity and anoxia
• Postnatal: meningitis and head trauma
© Cengage Learning 2016
The Two-Group Approach
• Organic group – there is a clear biological
basis
– Associated with severe and profound MR
• Cultural-familial group – there is no clear
organic basis
– Associated with mild MR
© Cengage Learning 2016
Risk Factors
• Four major categories of risk factors
– Biomedical
– Social
– Behavioral
– Educational
© Cengage Learning 2016
Causes
Risk Factors (cont'd.)
© Cengage Learning 2016
Inheritance and the Role of the Environment
• Genetic influences are potentially
modifiable by environment
• Genotype: a collection of genes that
pertain to intelligence
• Phenotype: the expression of the
genotype in the environment (geneenvironment interaction)
© Cengage Learning 2016
Inheritance and the Role of the Environment
(cont'd.)
• Heritability describes the proportion of the
variation of a trait attributable to genetic
influences in the population
– Ranges from 0% to 100%
– The heritability of intelligence is about 50%
• Major environmental variations affect
cognitive performance and social
adjustment in children from disadvantaged
backgrounds
© Cengage Learning 2016
Genetic and Constitutional Factors
• Chromosome abnormalities
– Down syndrome is usually the result of failure
of the 21st pair of the mother’s chromosomes
to separate during meiosis ► causes an
additional chromosome
• Fragile-X syndrome is the most common
cause of inherited ID
• Prader-Willi and Angelman syndromes
– Both are associated with abnormality of
chromosome 15
© Cengage Learning 2016
Genetic and Constitutional Factors (cont’d.)
• Single-gene conditions: inborn errors of
metabolism
– Excesses or shortages of certain chemicals
which are necessary during developmental
stages
– Cause of 3-7% of cases of severe ID
– Phenylketonuria results in lack of liver
enzymes necessary to metabolize
phenylalanine
• Can be treated successfully
© Cengage Learning 2016
Neurobiological Influences
• Adverse biological conditions
– Examples: infections, traumas, and accidental
poisonings during infancy and childhood
• Fetal Alcohol Spectrum Disorder (FASD)
– Estimated to occur in one-half to two per 1000
live births
• Teratogens increase risk of ID
© Cengage Learning 2016
Social and Psychological Dimensions
• Least understood and most diverse factors
causing ID
• Environmental influences and other mental
disorders account for 15-20% of ID
– Deprived physical and emotional care and
stimulation of the infant
– Other mental disorders accompanied by ID,
such as autism
• Parents are critically important
© Cengage Learning 2016
Prevention, Education, and Treatment
• Child’s overall adjustment is a function of:
– Parental participation, family resources, social
supports, level of intellectual functioning,
basic temperament, and other specific deficits
• Treatment involves a multi-component,
integrated strategy
– Considers children’s needs within the context
of their individual development, their family
and institutional setting, and their community
© Cengage Learning 2016
Prenatal Education and Screening
• ID related to fetal alcohol syndrome, lead
poisoning, rubella) can be prevented if
precautions are taken
• Prenatal programs for parents caution
about use of alcohol, tobacco, drugs, and
caffeine during pregnancy
© Cengage Learning 2016
Psychosocial Treatments
• Early intervention
– One of the most promising methods for
enhancing the intellectual and social skills of
young children with developmental disabilities
– Carolina Abecedarian Project provides
enriched environments from early infancy
through preschool years
– Optimal timing for intervention is during
preschool years
© Cengage Learning 2016
Behavioral Approaches
• Initially seen as a means to control or
redirect negative behaviors
• Association for Behavior Analysis (ABA)
Task Force advocates that:
– Each individual has the right to the least
restrictive effective treatment and the right to
treatment that results in safe and meaningful
behavior change
© Cengage Learning 2016
Cognitive-Behavioral Therapy
• Self-instructional training and
metacognitive training
• Verbal instructional techniques
• Teaching the child to be strategical and
metastrategical
© Cengage Learning 2016
Family-Oriented Strategies
• Help families cope with the demands of
raising a child with ID
• Some ID children and adolescents benefit
from residential care or out-of-home
placement
• The inclusion movement integrates
individuals with disabilities into regular
classroom settings
– Curriculum is adapted to individual needs
© Cengage Learning 2016